Geotechnical and Structural Engineering Congress 2016

Over the past two decades, blast resistant design of buildings has become increasingly prevalent, with most U.S. Government owned or leased buildings requiring some level of blast resistance. The number of buildings being designed for blast resistance has increased, resulting in precast pre-stressed concrete structural system becoming a common consideration for construction type. The blast response characteristics of some of these systems are not supported by available test data. One such system is load-bearing precast panels. While concrete has long been used for blast resistant construction, including building columns subject to axial load, blast response research on load-bearing concrete wall panels is extremely limited. A research program to gather response data and improve analytical models for load-bearing pre-stressed pre-cast concrete wall panels was funded by the Precast Concrete Institute to provide a better characterization of the blast response of this structural system. This paper will describe the experimental portion of the research program, focusing on the approach used in testing three different wall panel designs in shock tube tests that included static applied axial loading. Discussion will include the apparatus designed for application of the axial load and its capabilities, including changes in axial loading as the test specimens respond to applied blast loads. The axial force provided by the apparatus will also be compared to analytical predictions of axial forces for a building determined from finite element calculations. General effects of the axial load on performance of the panels compared to performance of non-load bearing panels will also be discussed in the paper.

Truck collisions with bridge piers can result in significant damage to the support pier and potentially lead to partial of full failure of the structure. This paper aims to study the structural response of reinforced concrete bridge piers subjected to vehicle collisions. Multiple parameters are known to affect the structural response such as pier diameter, transverse reinforcement spacing, vehicle impact velocity, pile cap height, and multi-pier configuration. This paper focuses on the effects of having single or multiple piers in the bent. Detailed finite element models of the single pier and multi-pier bent configurations have been developed. The truck models offered by the National Crash Analysis Center and the National Transportation Research Center are used to conduct this research. The finite element models are validated by comparing the results to available experimental tests. The bridge pier collision models are validated by comparing peak impact forces observed as well as checking the energy content of the whole system. The study suggests that a multi-pier bent changes the trend of absorption of kinetic energy, failure modes, and distribution of impact forces, especially for the lower impacting speeds. Although a multi-pier configuration results in higher impact forces but due to higher stiffness results in low lateral displacements, and higher resistance to shear and moment stress. The dynamic characteristics of the multi-pier bent also affects how the shear and moment forces are propagated within the pier.

This paper presents analytical tools to assess the performance of steel-plate composite (SC) walls subjected to blast and impact loads. These methods include P-I diagrams, design charts, single-degree-of-freedom (SDOF) models, and nonlinear finite element (FE) analysis. Each analytical method has been benchmarked to an experimental database which includes a wide range of design and load parameters. The paper also includes examples and recommendations to use these tools to assist in the design of protective structures.

The unfortunate events of September 11th, 2001 have prompted transit agencies to consider potential terrorist attacks against underground tunnels as part of the design criteria for such structures. Due to the confining nature of those tunnels, and the potential to inflict physical and psychological harm to the public, the underground tunnels might be considered attractive targets by would-be assailants. The blast response of the tunnel structure is influenced by the medium surrounding the tunnel. For example, it has been found that significant damage can be caused by waterborne bombs due to the thrust induced by hydraulic forces. Furthermore, the properties of the surrounding soil will not only influence the tunnel response during a blast event, but might also affect the infiltration of water and debris into the tunnel network should the tunnel walls be breached. This article will discuss blast vulnerability of underground tunnels, blast damage assessment considering nonlinear soil-structure and fluid-structure interactions, and finally some of the blast mitigation strategies will be presented. A risk-based methodology is presented as a tool to facilitate and justify the selection of appropriate blast mitigation strategies.

The PHX Sky Train project is a key linkage in the City of Phoenix, Arizona, Department of Aviation’s multimodal facility which integrates Phoenix Sky Harbor Airport with the City’s eastern transit (Valley Metro) hub. This local project consists of a series of different bridge types, built to support the operation of the airport’s new transit system, as it stretches from the multi-modal center and 44th St. to the Phoenix Sky Harbor Airport Terminals 3 and 4. These include: (1) steel girder superstructures, (2) cast-in-place post-tensioned, (3) a precast, pre-stressed post-tensioned, pedestrian bridge along with (4) a signature cast-in-place structure spanning an airport taxiway. Along with these differing bridge types, came complex geotechnical requirements and in-situ conditions. The design of the large diameter drilled shafts supporting the elevated guideway was complicated by space constraints, due to the elevated guideway alignment being situated adjacent to existing buildings, retaining walls, a baggage cart tunnel, and between an existing retaining wall and an existing high-pressure jet fuel line, all of which had to remain in service during construction. The foundation system supports relatively high axial loads, lateral loads and moments due to the height of the guideway above the ground surface, where it needs to pass over existing concourse walkways, bridges, a taxiway and buildings. The extreme design requirements, together with difficult ground conditions at the site, resulted in several challenges in the design of the deep foundation system. Built under the construction manager-at-risk (CMAR) contract structure, the project was built in multiple phases to accommodate the schedule of the METRO opening in winter 2008. Its design was a puzzle of a series of separate contracts that required tight coordination between multiple designers and stakeholders. Multiple system and design coordination meetings were held by the designers in conjunction with the client (City of Phoenix, Department of Aviation) and the selected contractor. Attendees will take away both technical and managerial lessons-learned from this complex transportation project. Complex environmental demands required a series of innovative design solutions. Moreover, the tight, multi-phase schedule and CM@R design paradigm presented many management challenges which will be discussed.

This paper presents a novel method for presenting the concrete bridge deck condition assessed by multiple nondestructive evaluation (NDE) technologies using a three-dimensional visualization program, NDEFuse. Six types of NDE data can be visualized: (1) impact-echo data for mapping and describing the depth and severity level of concrete delamination, (2) ultrasonic surface wave data for concrete quality (elastic modulus) assessment, (3) electrical resistivity for the description of corrosive environment and estimate of the corrosion rate of steel reinforcement, (4) mapping of top rebar layer and (5) ground penetrating radar condition assessment data, and (6) high-resolution deck surface image for documenting signs of deterioration, previous repairs, and surface wear. The 3D visualization platform integrates and visualizes the six NDE results in a very intuitive way. Correlations between the different types of NDE survey results were established visually in a 3D space utilizing the developed program.

An automated test frame was designed and built in which concrete blocks with artificial defects or testing problems can be tested by various NDT methods. The focus of the measurements carried out on a tendon duct block was to see how precisely the tendon ducts can be located in the block and if the different areas with different grouting states (empty, fully, or half-grouted) can be identified. Ultrasonic pulse-echo successfully located the ducts in their lateral position as well as in depth. Even the different sizes of the ducts can be estimated from the results. In the impact-echo data, the lateral positions of the ducts can be determined based on a shift of the measured thickness towards an apparently increased thickness at the location of the duct. However, this means that the duct cannot be located in depth. All four ducts were partly filled with grout to simulate voids in the grout. Although there are certain indications in the ultrasonic as well as in the impact-echo data that are correlated to the actual position of the voids, the indications are rather vague. Very likely this was due to a fabrication issue: the grout debonded from the wall of the duct thus making it impossible to distinguish between grouted and ungrouted parts of the duct.

The objective of this paper is to revise the effective slab width of integral bent cap beams in reinforced concrete box-girder bridges. Currently, a conservative code-based value of 12 times the slab width plus the cap beam width is used to define the beam’s top and bottom flange widths to account for the box-girder slab contribution as part of the cap beam analysis and design. A comprehensive experimental study was utilized to revise the integral bent cap beam effective slab width for more accurate design and capacity estimation. Two large-scale column-cap beam-box-girder bridge subassemblages were tested under combined vertical and lateral loading. The first specimen was tested using quasi-static cyclic loading and the second was tested using hybrid simulation earthquake loading. A strain-based approach was used to estimate the bent cap effective slab width at different loading levels. The study concluded that 12 times the slab width is a conservative estimate for the box-girder slab contribution to the bent cap stiffness and capacity, and 18 times the slab width is a more accurate representation.

This paper introduces an innovative joint element to model the hybrid sliding-rocking (HSR) joints utilized in substructure columns of HSR segmental bridges. HSR joints allow both sliding and rocking of the connected segments with respect to each other, which makes their simulation challenging. The proposed element is capable of capturing the interaction of the adjacent segments by combining a force-based (FB) beam element formulation with a hysteretic friction model and an empirical formulation for joint rocking. The empirical rocking formulation is incorporated at the element mid-length, where rocking occurs, through adaptive modification of the corresponding integration weight, which is varied throughout the analysis as the segments’ contact depth changes. The results obtained from the numerical simulations of a HSR pier using this element are in a good agreement with the past experimental data.

This paper addresses the wind actions on cable-supported bridges including the relevance of wind tunnel testing. Background is given on flutter and vortex-induced vibrations, from which wind tunnel testing is made necessary. References will include wind actions on long span bridges in the United States, Canada, Norway, and Denmark. A long term experience have shown that section model wind tunnel tests may be efficient and accurate when predicting wind-induced vibrations on bridges. The combination of full-scale measurements and experimental wind tunnel data complement each other giving the most accurate wind-induced response of the structure. For very streamlined bridges often used for European cable-supported bridges, vortex-induced vibrations measured in the dynamic test rig may depend on the Reynolds number and hence the length scale of the section model. Experimental data is taken from 1:10 and 1:50 section model tests performed in large and small boundary layer wind tunnel facilities with an h x w cross section of 3.0 x 2.5 m and 1.55 x 1.75 m, respectively. Low Reynolds numbers simulated with a 1:50 scale model give much larger vibrations than found for intermediate Reynolds numbers simulated with a 1:10 scale model. This behavior is similar to the behavior of circular cylinders. Full-scale measurements performed on Great Belt Bridge show a good correlation with wind tunnel tests on scale 1:50 section models.

Damage to bridges has been observed during many recent earthquakes despite the fact that the structure was designed according to model codes. Pier foundations can be made robust by using pile groups and an efficient pile cap. However, in that case the relatively weak components are the abutments, which act as retaining walls during a significant seismic event. Previous studies have shown that there have been several incidents of damage to abutments and shear keys due to pounding. This paper studies the performance of an existing multi-span curved bridge supported on rigidly capped vertical pile groups which pass through a deep layer of soft clay. Soil-structure interaction (SSI) between the pile group and soil is idealized as linear springs in two perpendicular horizontal directions. At the expansion joints and abutments, steel shear walls are provided to improve the performance and concrete shear keys are utilized to restrain the lateral movement of the bridge girders and bridge deck during large earthquakes. The earthquake response of the bridge with SSI is obtained under unidirectional earthquake excitations at various angles. A seismic retrofit scheme is implemented at the abutments, using buckling restrained braces (BRB) at each girder which are parallel to the deck length, to prevent pounding damage. BRBs are idealized using bilinear plastic link elements with a backbone curve adopted from experimental data. Time history analyses are performed for historical earthquakes. It is observed that the soft soil surrounding the piles has a significant effect on the dynamic response of the bridge; in addition, the bearing displacements are underestimated if SSI is ignored. Non-linear analysis shows that pounding damage to the abutments and the deck can be prevented by using a combination of properly designed BRBs. Incremental dynamic analysis with scaled ground motions shows that the relative displacement between the deck and the abutment is reduced up to 50% after implementing a retrofit with BRBs. Concrete shear keys are also protected against damage due to the reduced lateral displacement of the deck.

Bridge abutments supported on cast-in-drilled-hole (CIDH) piles embedded in mechanically stabilized earth (MSE) retaining walls are becoming increasingly common in California. Pile behavior under lateral (e.g., earthquake) loading for this relatively new abutment system is currently not well established. To that end, three-dimensional finite element modeling is undertaken for a representative pile-supported MSE abutment with wrap-around MSE walls retaining the approach embankment on the two longitudinal sides and beneath the bridge deck. In this configuration, seven 0.9-m (3-foot) diameter CIDH piles in a single row extend 7.6 m (25 feet) above native subgrade inside the MSE wall, and connect to the abutment footing. The piles are located close to the wall face, at a longitudinal clearance of 0.46 m (18 inches). Lateral pile top loading is applied to the finite element models in the longitudinal and transverse directions separately, in two sets of analyses. Under longitudinal pile top loading, the response of the single row of piles is found to be dictated primarily by the properties of the MSE reinforcement material. In contrast, the response under transverse loading is found to be governed significantly by the soil resistance in between the seven piles. For use in repetitive design iterations, simplified beam-spring analysis procedures are developed, similar to those used for ordinary level-ground lateral pile analysis. Design recommendations based on the simplified models are found to compare well with results from the finite element analyses.

Permanent casing is commonly used for drilled shafts that extend through very soft soils to reach an underlying stable stratum. However, steel casing will generate a reduction in skin friction resulting from the use of permanent casing compared to concrete placed directly against the soil. The side resistance reduction factors due to the steel casing relative to concrete shaft can vary depending on type, length, and installation method of casing. A large load test program was performed for the Sir Solomon Hochoy Highway Extension Project in Trinidad and Tobago. A total of eight drilled shafts were constructed and tested. The drilled shaft used a vibratory installed steel casing as a construction aid in soft to stiff clay and loose to medium dense sand stratum. A program of dynamic load tests was conducted and analyzed using a combination of CAPWAP and SIMBAT methods to measure the axial response of the drilled shafts. The load test results demonstrated that the case zone of the shaft experiences a reduction in side resistance as compared to an uncased shaft section. This paper presents the site conditions, construction methods, load test results, and comparison between predicted and measured side resistance of the test shafts. The load test program was structured to help optimize side resistance reduction factors resulting from the use of permanent steel casing.

The behavior of the skewed extended shear tab connections has been studied using computational nonlinear mechanics. While the unstiffened skewed extended shear tab connections have been investigated in a previous study, this study addresses failure modes and the analyses of different configurations of stiffened skewed extended shear tab connections using the finite element analysis (FEA) ABAQUS. The finite element model is verified with experimental results from tests performed on extended shear tab connections. Results showed that the vertical connection displacement decreases slightly with the increase of the connection orientation. Moreover, it was observed that the type of supporting member highly affected the torsional behavior of these connections. For connections with a column as a supporting member, it was proven that the torsional stiffness increases with increase of the connection orientation except for connections with three bolts, where the torsional stiffness decreases as the connection orientation increases at a high level of shear force. On the other hand, it was detected for connections with a girder as a supporting member, the torsional stiffness decreases with the increase of the connection orientation. However, the same failure modes were obtained from the orthogonal and skewed configurations.

Current design provisions for CMU shear walls are largely derived by empirically fitting equations to experimental data. The disadvantage of this approach is that, generally, existing experimental data is biased towards relatively small, fully-grouted, walls without openings. CMU walls used in practice, however, are frequently partially grouted and contain openings. Thus, there is a need for a theoretical approach to determine the capacity of CMU shear walls. Strut-and-tie modeling could potentially address this need. The purpose of this paper is to assess a strut-and-tie modeling approach for the design of squat partially-grouted CMU shear walls. To accomplish this goal, the author compile a database of 25 fully-grouted and 11 partially-grouted experimentally-tested CMU walls. Strength predictions for these walls are determined in accordance with the current masonry design code (MSJC 2013) and a strut-and-tie approach similar to what is in the concrete design code (ACI 318); and a comparison is made between predicted and experimental capacities. Based on the results of this analysis and considering the limited number of experimental results, the author found that the strut-and-tie modeling approach performed statistically similar to the MSJC provisions for fully-grouted walls and significantly better than the MSJC provisions for partially-grouted walls. The implication of these results are that, in general a STM procedure could potentially be used to adequately predict the capacity of a squat CMU shear wall.

FRP (fiber reinforced polymer) composite retrofit is a practical method for increasing the strength of historic URM buildings. Several materials for FRP upgrading are now available, including using FRP made of glass, aramid, basaltic, and carbon fiber, various resins such as epoxy, polyester, and vinyl ester. In addition to the choices for materials, different retrofit techniques are available, including externally bonded, near-surface mounted, and mechanically anchored FRP. Each of these has strengths and weaknesses for use in historic buildings, related to durability, mechanical compatibility, ease of installation, chemical suitability, seismic ductility, strength, reversibility, and cost. This paper will describe the differences between the various methods of FRP retrofit used for historic building strengthening, describe case studies of FRP installation and performance for historic buildings, and make recommendations for FRP retrofit in relation to the “Standards for Historic Preservation” by the National Park Service.

The direct analysis method is applicable to all types of framed structures, and therefore has an advantage over other, more limited, stability analysis methods. Research studying stability of full scale trusses subjected to multiple bracing scenarios and loadings has been conducted at the University of Colorado Denver. The first part of the research was developing a 3D structural analysis model using a second order direct analysis to predict a critical buckling load, compared to results of stability experiments of full scale bar joists. The comparisons were used to validate the direct analysis method applied to the models. The bar joists used in the stability experiments inherently have imperfections, while notional loads were used in the computer modeling to represent geometric imperfections. Results from the full scale bar joists tests were shown to validate computer modeling direct analysis results when appropriate initial conditions were applied.

This research investigates an innovative “unibody” light-frame design which utilizes the flexibility/versatility of fibrous composites in construction, as well as the sustainable feature of agricultural waste plant-fiber materials. Unlike conventional light-frame constructions, where ply-wood or light-gauge steel sheathings are installed onto the supporting frame though fasteners, the building envelope components proposed in this research were “cast-in-place” to form a monolithic conformation. The mechanical performances of the composing natural/synthetic hybrid fiber materials were investigated in this study, in conjunction with the feasibility of the associated construction method. Furthermore, the structural performances of this new structure form and its ability to resist natural hazards were studied through experimental tests and the results were compared to those of conventional light-frame structures. The results indicate that the innovative monolithic design has enormous potential to offer enhanced and tunable structural performance (i.e., structural integrity, ductility) of light-frame building structures, as well as to provide superior energetic properties of the building envelope.

Superelastic shape memory alloys (SMAs) are promising materials for seismic applications since they have the ability to not only dissipate energy but also restore their original shape after large deformations. This study aims to develop numerical models of shape memory alloy rings designed as a new seismic damping system for building structures. This damping system is a tension-only concentrically braced device consisting of an SMA ring and four cables. The full-scale bracing system is tested under cyclic loading. The experimental results are then utilized to calibrate an Abaqus finite element model, which is then used as the basis of a parametric study to investigate the relations between the seismic performances and geometric dimensions of SMA rings. The results of this parametric study can be used to construct macro models of SMA devices in existing finite element frameworks.

Site characterization data is provided to a contractor or designer for the bidding and potential implementation of a contract. The data is developed through various techniques and is meant to assess the stratigraphy, composition, and properties of subsurface materials which are inherently variable. From a geotechnical engineer’s perspective there is uncertainty in the subsurface. If a contractor encounters subsurface materials which are different or not identified in the site characterization data, a differing site condition clam is filed. From a contractor’s perspective there is risk in constructing in the subsurface. Although uncertainty and risk are related, the processes of site characterization and subsurface design and construction must not be entangled. Contractors and designers utilize uncertain subsurface data developed through geotechnical site characterization processes to design construction sequences and structural components in the subsurface. Risk can only be realized through design and construction. Suggestions for updating the site characterization process to reduce uncertainty and thus minimize risk are discussed.

Cold-formed steel framed shear wall sheathed with corrugated steel sheets is a promising shear wall system for low- and mid-rise constructions at high wind and seismic zones due to its advantages of non-combustibility, high shear strength, and high shear stiffness. A series of full-scale shear wall tests on corrugated sheet steel shear walls have been conducted at University of North Texas. This paper presents the dynamic model in OPENSEES and incremental dynamic analysis on one two-story and one five-story cold-formed steel framed building. The analysis results provide a systematic assessment of the building performances subjected to earthquake loads.

Seismic response factors do not offer uniform margin of safety and economy of buildings for different seismic regions. To verify these factors, four high-rise regular steel buildings, ranging from 8 to 20 stories are selected and designed according to current design codes. These factors are estimated using a number of inelastic pushover analyses (IPAs) and incremental dynamic analyses (IDAs), and their respective safety margins are assessed. The results indicated a possibility of increasing design response factors. The selected buildings are redesigned and their performances are assessed and verified using the proposed increase in seismic design response factors. Cost comparison between the code designed buildings and the proposed seismic design factor buildings is made. The proposed study provides comparisons of seismic response factors between the code-designed buildings and alternative proposed design for the range of the selected buildings along with their economic benefits. The recommendations of this study may provide practical insights to the designers and stake holders to achieve more cost-effective and optimistic designs on a wide range of high-rise steel buildings.

A wide set of nonlinear dynamic finite element (FE) simulations is presented and discussed to highlight peculiar behavioral aspects in the seismic response of high-rise mega-braced frame-core buildings. In detail, 45- and 75-storey 2D frames, extracted from 3D case study structures composed of an internal two-way braced core, were designed according to European rules and then analyzed numerically, using inelastic force-based fiber elements to model structural members and mechanical idealizations to reproduce the behavior of bolted beam-to-column joints and welded gusset-plate connections. Out-of-plane imperfections of braces were explicitly included in the simulation to permit potential buckling mechanisms in both braces and gusset plates. Global and local performance of mega-frame systems and key structural components were investigated and the effects of bracing systems and outriggers/belt trusses were quantified. Sensitivity to the structure height was explored comparing the response of the two case study steel moment resisting frame (MRF) structures examined.

In the past earthquakes, heritage buildings have sustained severe damage and collapse in recent earthquakes, including in Italy (2009), Haiti (2010), and New Zealand (2011). For these buildings, the main vertical and lateral load bearing members are typically use variations of unreinforced masonry stone/rubble walls. These walls have little ductility and are susceptible to in-plane and out-of-plane failures that can result in building collapse. The situation is more pronounced in Haiti for heritage structures due to poor quality of design and workmanship. Heritage buildings were significantly damages in Haiti in past earthquakes (including the 2010 event). A proposed mitigation strategy combining seismic isolation and superstructure intervention was used to upgrade selected cathedrals in Haiti. The proposed method significantly reduces the level of seismic excitation acting on the existing walls and limits the superstructure retrofit, and thus preserves the historical features of the structures. Application of this technique to two cathedrals in Haiti is presented.

In this study, numerical analyses are carried out in hypothetic existent hospitals located in the lakebed zone of Mexico City. First, the performance of conventional hospitals is assessed using incremental nonlinear dynamic analysis with multiple earthquake records. Then, the hospitals are upgraded using buckling-restrained braces (BRBs) in order to explore the benefits of using these devices in the buildings. The results show that BRBs reduce significantly the dynamic response parameters on the hospitals. It is also observed that BRBs reduce both the probability of collapse and of loss of functionality; which are of paramount importance in these facilities. Finally, a parametric study is conducted in conventional and dual SDOF systems in order to determine the period range on which existent hospitals, located in the lakebed zone of Mexico City, may be benefitted from being upgraded using BRBs.

Major engineering, procurement and construction/construction management (EPC/EPCM) projects often include large-scale MSE walls. These walls are used in mining and power projects (around crushers), infrastructure projects (roadway embankments), etc., and are required to meet strict performance specifications. Wall malfunction/failure can significantly impact the project. Thus, design and construction of such MSE walls require close coordination between the EPC/EPCM contractor and the MSE subcontractor/contractor to ensure successful outcomes. An extensive literature search conducted to identify and review case histories dealing with MSE wall malfunctions and/or failures is presented. An anonymous MSE wall survey was prepared and sent to MSE wall specialty subcontractors/contractors and other geoprofessionals. They were asked to share their knowledge and experience with the design, construction, and performance monitoring of MSE walls. The survey consisted of questions and requests for feedback describing the work process employed for the design and construction of MSE walls as well as positive and negative experiences. A summary description of the survey along with a summary of the evaluation of the survey responses is included here. The survey responses provided unique, unpublished information and also served to complement the literature search. Results of the literature search were combined with the survey responses to identify opportunities for best practices and lessons learned.

The shape of soil arch is a key parameter in modern design of piled embankment. Design guidelines for piled embankment in the Netherlands, Germany, and the United Kingdom have been updated in 2011 to consider the improved understanding of the arching mechanism. Recently in Korea a national research project on the design code of the geosynthetic-reinforced piled embankment is being conducted. As part of the project, a series of finite element simulations have been performed. Numerical study mainly focuses on the visualization of soil arch under various different parametric conditions. By taking the local extremes in the vertical distributions of the vertical stress obtained from numerical simulations, the shapes and sizes of the soil arch zone were estimated. Numerical results show that the size of the dome-shaped soil arch zone remains constant in variation of the cohesion and friction angle of the fill material. However, the stiffness of the soft material between piles has a significant influence on the height of the soil arch zone. For the sufficient low stiffness of the soft material, the height of the dome-shaped soil arch zone is approximately 42% total embankment height.

The project’s objective was to investigate and remediate distressed MSE walls at a highway interchange system with multiple direct connectors supported by MSE walls. The contract scope was to develop the construction plans, specifications and engineer’s estimate and provide engineering support during construction. The investigation utilized advanced in-situ testing, laboratory testing, and detailed modeling/analysis to determine the root cause of distress for walls as well as secondary distress features that have contributed to the walls degraded performance. Remediation alternatives presented to the client with their cost and value helped develop the comprehensive repair plans. The holistic design approach addressed structural, drainage, paving, geotechnical, roadway, and environmental problem areas. This presentation will discuss major design items such as void remediation within the reinforced zone of the MSE wall, installation of underdrains in an existing wall, and restoration of flexibility to the MSE wall system. Additionally, the presentation will highlight construction issues encountered and lessons learned for construction plan development and communication with the different teams involved in the construction.

The William Eckhardt Research Center, a 25,500 square meter (275,000 square foot) building, was constructed on the University of Chicago campus. The structure features five floors above grade, a basement and a sub-basement. The proposed depth of excavation to construct the basement varied between 15 and 16.5 meters (49 and 54 feet). A diaphragm wall was selected as the earth retention system and permanent foundation wall due to its cost effectiveness and ability to minimize groundwater infiltration into the facility after construction. The urban, congested nature of the project location presented many design and construction challenges. The research center is located in the heart of the University of Chicago campus next to two active streets containing many utilities critical to the operation of the University, as well as two active research facilities, which house experiments that are highly sensitive to vibrations. To address these various challenges, multiple techniques were required to support each side of the excavation, including tiebacks, internal bracing, and micropile mid-span supports. The neighboring University research structures required underpinning which was accomplished using a combination of micropiles, tie downs, and jet grouting. Inclinometers and settlement points were installed and monitored throughout the braced excavation construction. The data collected showed negligible settlements, and horizontal deflections of less than 2.1 centimeters (0.8 inches) across the profile of the wall.

In 2012, the Novartis Institute for Biomedical Research embarked on a $600 million expansion of its Cambridge, Massachusetts Campus with the addition of a 550,000 square foot complex which includes multiple levels of underground space. To excavate to the maximum depth in excess of 45 feet, the contractor faced several logistical challenges presented by the congested, urban location. These challenges included the shear size of the excavation, which occupied an entire city block, the presence of very soft clay deposits, the close proximity to adjacent buildings and varying structural systems and slab elevations. A support of excavation (SOE) system was designed which consists of a combination of deep soil mix wall and steel sheet piling to support a total excavation area of about 3.2 acres (138,500 sq ft). Since the use of tiebacks was limited due to the site location, the SOE was mostly supported by internal bracing; with single strut lengths reaching 240 feet. Finite element models were developed to account for soil non-linearity, SOE stiffness, and varying depths of excavation. With strut loads up to 1,200 kips, an instrumentation system provided real time data acquisition of the loads in the bracing and deflections of the SOE. The monitoring data were comparable to the stresses and deformations predicted by finite element model.

The new home of the Berkeley Art Museum and Pacific Film Archive combines a challenging adaptive reuse project with a unique auditorium addition. Located on a tight parcel of land in downtown Berkeley, California, the site is bounded by three city streets, an operating bank, an occupied apartment building, and an existing parking garage. The architectural and structural scope on the project necessitated an elaborate suite of shoring systems to facilitate the downward and outward expansion of the existing facility on the site, including soldier beams and tiebacks, soil nail walls, concrete buttresses, braced-frame buttresses supported on drilled piers, hand-mined underpinning piers, and hydraulic jacking of steel support structures. The final design package reflected flexibility from the design team and versatility from the contractors, keeping all options open and ensuring the right shoring systems would be used in the right places.

A rectangular starter trench measuring 220 feet long by 23 feet wide and a 24-foot diameter, 12-sided receiving shaft were built in order to accommodate launching and removal, respectively, of an earth pressure balance (EPB) tunnel boring machine (TBM) which was used to construct a subaqueous water supply tunnel in New York City. For the TBM starter trench located in Staten Island, the 4-foot wide slurry walls were excavated with a clam shell and a hydromill to a depth of approximately 90 feet through fill and glacial soils and into competent rock at the western portion of the excavation, and to 107 feet into decomposed bedrock at the eastern portion. During slurry trench excavation, the work was closely monitored by performing time-controlled slurry tests and examining muck conditions from a slurry separation plant. Also, vertical and horizontal deviations of the slurry trenches, rebar cage placement, and the concrete pour were closely monitored and inspected to maintain construction within the design tolerances. For the TBM receiving shaft in Brooklyn, the 3-foot wide slurry walls were excavated to a depth of approximately 155 feet mostly with a hydromill. Difficult ground conditions due to uncontrolled fill including wood timber and concrete debris, and glacial sand with boulders were overcome with intermittent use of a clam shell and large chisel. The rebar cages of the primary panels were fabricated in a “concave up” shape and the secondary panels were constructed in a rectangular shape. Together they formed the circular shaft shape. Due to the slurry wall depth, three sections of the rebar cages were spliced while inserting into the slurry trench. The TBM break-in and break-out portion of the slurry walls were reinforced with fiber-glass rebar.

The Second Avenue Subway is currently under construction in Manhattan, New York. Spanning seven city blocks, the cut-and-cover station at 96th Street is the largest station in Phase 1. The station excavation is up to 68 feet deep and is typically within 20 feet of adjacent buildings. The station straddles areas of rock and deep soil at its invert and requires various forms of ground support, including both temporary and permanent secant pile and slurry walls. Construction was undertaken in a dense urban environment, adjacent to fragile buildings, with significant underground utility and traffic maintenance restrictions. Excavation and construction of the permanent earth support was recently successfully completed. This paper reviews the design and construction methodology for the ground support systems adopted and discusses the interfacing and construction challenges faced in a highly constrained environment from the perspectives of both the designer and contractor.

Deep excavations associated with the construction of underground parking garages for major corporate buildings create significant challenges for geotechnical engineers, especially when the subsurface material consist of non-controlled fill. This paper provides a detailed description of a project located in Santa Fe, Mexico City, Mexico, where two corporate towers with 26 and 12 stories and 8 basement levels were built on a 1970s landfill site. Based on the maximum depth of excavation and local restrictions on deformations for major road arteries located in close proximity to the project site, the retaining system selected for the project consisted of a diaphragm wall reinforced with post-tension anchors. In addition to geotechnical drilling and sampling, results of three full scale pull-out test completed at the north end of the project site are discussed. From the load tests, cable elongations were recorded to be less than 1% of the bonded length of the anchors.

As part of the PHX Sky Train project at Phoenix Sky Harbor International Airport in Phoenix, Arizona, the Taxiway S and T undercrossing consists of a depressed on-grade guideway section and service road which will be constructed using top-down construction methods to construct an additional end-span and new abutment at the two existing aircraft taxiway bridges. The soil conditions in this area generally consist of alluvial sand, gravel and cobbles (locally known as SGC) deposited by the nearby Salt River. Based on the anticipated loading conditions and the difficult ground conditions and after studying several alternatives, it was decided to design a drilled shaft soldier pile system which can be used for both foundation support of the Taxiway S and T undercrossing bridge abutment, and as the earth retention system for excavation support. The high loading conditions generated by aircraft loads are proposed to be carried by 4.5 foot diameter drilled shafts spaced 10 feet on center. To resist the lateral loads, the construction of the new bridge abutment included constructing anchor slabs behind the abutment and installing permanent ground anchors through sleeves in the abutment caps before excavating the soffit fill supporting the new cast-in-place bridge deck span. Numerical analyses were performed to predict the short- and long-term behavior of the new abutment wall. The results from the numerical modeling using PLAXIS software showed that the proposed solution is deemed adequate to provide the needed capacity with an acceptable factor of safety, along with acceptable deformation. Based on survey monitoring of the new abutment wall performed during construction, the recorded lateral movement of the wall is significantly below that calculated by numerical analyses

Structural stiffness of a retaining wall, properties of the foundation soils, and the construction sequence, including order of placement of fill in front and back of the wall, affect movements and hence the development of active and passive earth pressures. Retaining walls considered in this paper are the traditional reinforced concrete type usually constructed along highways and dam spillway structures – the highway wall is a simple cantilever and the spillway wall in an earth dam is a counterfort. Another type of earth retaining structure considered is an unconventional type, which was used during construction of a second large-diameter reinforced concrete siphon alongside an existing siphon of similar proportions for water conveyance on a hydro project. Results of numerical modeling for the highway retaining wall are compared with measured data. For the spillway and the siphon structures, only numerical analyses are included, as these structures were not instrumented. Practical significance of the information included in the paper are: (a) both the structure and the soil on which it is founded form an integrated system that needs to be analyzed as such for meaningful results; (b) interfaces between the soil and structure, where separation and slip can occur, should be included in numerical modeling; and (c) sequence of construction starting with the initial excavation, and construction sequence including placement of the fill in lifts, should be simulated.

Wolf Creek Generating Station, a nuclear power plant located in central Kansas, recently completed a project to improve the essential service water (ESW) piping system that supplies water to cool the reactor. Part of the project involved the construction of retaining walls in the cooling water reservoir adjacent to the existing ESW pumphouse to retain new earth embankments. Site conditions and operational restrictions dictated the use of a wall system that would not interfere with the pumphouse or encroach on the reservoir, that could be constructed without temporary cofferdams or dewatering, and that could meet the design and construction quality assurance requirements for nuclear safety-related structures. To meet these requirements, a cantilever retaining wall system consisting of nearly-tangent large-diameter rock-socketed drilled shafts was designed to resist conventional earth retention and bulkhead wall loads as well as forces associated with tornado-generated missiles. The steel-cased reinforced concrete shafts were installed from a barge, a cast-in-place concrete cap beam was built to tie the shafts together, and rock fill was placed behind the walls to form the new embankments.

Terrestrial Lidar scanning has the potential to be a powerful tool for condition assessment, as-built verification, and forensic investigation of MSE and GRS structures. This paper presents a method to extract vertical profiles of wall facing position from a lidar data set. For profiles obtained at one time, the profiles can be compared to each other to check the vertical and horizontal wall alignment or they can be compared to the construction drawings and specifications. Profiles of the same location obtained at different times can be compared to extract the settlement and lateral displacement of the wall facing. A series of laboratory tests are described that were used to conclude that the texture and reflectivity of split-block facing does not interfere with the ability of the lidar to achieve the measurement accuracy specified by the manufacturer. The proposed data processing work flow is demonstrated using two full-scale walls.

Service state behavior of mechanically stabilized earth (MSE) walls are highly dependent on the interaction of soil, reinforcement material, reinforcement spacing and facing selection and connection. A numerical model simulating the complex behavior of reinforced soil walls using finite element method developed to evaluate the behavior of a reinforced retaining wall with modular block facing for a variety of design options, including reinforcement selection and density. A nonlinear elastic-plastic constitutive soil material model was calibrated to experimental plane strain test data, while the performance of the wall model was validated against full-scale laboratory testing of an identical geosynthetic reinforced wall performed in available literature. Important behavior, including lateral earth pressures and deformations were monitored for various configurations to highlight design considerations in context of MSE walls. It was found that service-state performance of the reinforced soil wall was highly dependent of reinforcement type and spacing.

The facing of an MSE wall is composed of a number of discrete facing units (i.e., modular blocks or pre-casted concrete panels), which are connected to reinforcement (geosynthetic sheet or metallic strips) to provide lateral confinement for the reinforced soil zone. The adjacent facing units interact with each other through friction, and/or a connector or shear key. The current design methods checks the internal and external stabilities separately and does not consider the effect of facing unit on the stability of an MSE wall. This study, based on a series of numerical simulations and limit equilibrium analyses, investigated the possibilities of compound failure of two-tier MSE walls for various wall heights and setback distances. In the numerical modeling, the facing units was modeled a series of discrete blocks that interacts with each other through interfaces which allow relative movements but will yield once the shear stress exceeds the limit. Both the numerical simulations and limit equilibrium analyses show that critical slip surface may cut through the bottom region of the reinforced zone to form a compound failure plane. However, the critical planes obtained from the numerical simulations go through the facing, but, in contract, as the limit equilibrium analyses cannot consider the effect of the facing the obtained the critical plane is significantly different in terms of shape and location.

Experimental and numerical studies of the seismic response of a deep, stiff basement structure were motivated by the fact that the current seismic design methodologies based on previous works predict very large dynamic forces in areas of high seismicity. The experimental program consisted of a geotechnical centrifuge model with a basement structure embedded in cohesionless backfill. The numerical analyses sought to replicate the results of the centrifuge experiment and to validate the use of numerical analyses for the prediction of expected behavior. Overall, the results of this study show that the Mononobe-Okabe method of analysis provides a reasonable estimate of the expected response of stiff basement structures provided depth-averaged design accelerations are considered.

A 24m length retaining wall failure during an extreme rainfall event led to remedial measures of that failed section. However a 100m length intact section was also deemed to be inadequate. Back-analysis of the failed section using saturated soil mechanics and a single stage failure is used to obtain design parameters. These are then transposed to the existing wall and leads to the conclusion of replacing the 100 metres of visibly intact wall, when the back-analysis ground parameters and water level is superimposed on the higher wall heights. Using unsaturated soil mechanics in the back-analysis and a staged failure approach leads to a different conclusion – that the intact wall does not require stabilization. This case study discusses how the choice of analytical models can lead to different conclusions.

Buildings with deep basements became more commonplace in Southern California because of the elimination of a maximum building height limitation of 13 stories in the City of Los Angeles in the late 1950s. With the tall buildings often came deep basement structures to accommodate for the required parking for these larger occupancy structures. Southern California geotechnical practice provided design pressures for basement walls that were based on active earth pressure conditions rather than at rest pressures. Design of deep basements in Southern California that considered seismic earth pressures were not common until after the mid-1990s. Design for at rest pressures for basement walls in Southern California did not occur until the adoption of the California Building Code in 2007 that reflected the earth pressure requirements of the International Building Code that specified at rest earth pressures for restrained walls. There have been a significant number of tall buildings with deep basements constructed in Southern California with depths of up to 60 feet and even up to 100 feet below ground surface. Many of these were completed before the 1994 Northridge earthquake and some even before the 1971 San Fernando earthquake. Strong motion instrumentation was installed in some of these buildings. This paper will review the earthquake motions recorded in the basements of selected buildings in these two earthquakes and also examine the earth pressures which these buildings were designed for and comparisons with the present practice are made.

The Wilshire Grand Redevelopment project in downtown Los Angeles includes the demolition of a 16-story hotel built in the early 1950s and the construction of a new 73-story tower that will be the tallest building in the western United States. The construction of the basement and foundation of the new tower required excavation up to 93 feet (28 m) deep. One side of the basement excavation, with an excavation height along that side of up to 57 feet (17 m) required placement of shoring within about 6 feet (1.8 m) to 10 feet (3.0 m) horizontally from a 400-foot-long (122 m) section of the Los Angeles Metro Red Line subway tunnel. The temporary shoring support system for the Wilshire Grand deep excavation consists of soldier piles spaced generally at 8 feet on center with multiple levels of tieback anchors which extended above the subway tunnels. The bottom-most level of bracing consisted of rakers supporting walers attached to the soldier beams, because a bottom-most level of tie-back anchors could not be installed due to the presence of the subway tunnels. The shoring monitoring included periodic surveying, slope inclinometers, load cells on tie-back anchors, and strain gauges on raker braces (raking struts). Deflection monitoring was also performed on the interior of the Red Line tunnel. The paper presents a description of: (1) deflection and earth loading criteria for design; (2) geometric constraints of shoring design; (3) limitations on tie-back shoring due to limited easement width; (4) comparison of deflection and load from design criteria using results obtained from geotechnical instrumentation; (5) raker preloading methodology; (6) temperature dependence on raker loading; and (7) deflection distribution as a function of distance from shoring wall. Lessons learned regarding preloading of rakers and deflection of shoring and retained earth will be described.

An experimental and theoretical evaluation of crack evolution in a clay sample subjected to desiccation is presented. The desiccation cracking of the clay sample was recorded using photographs and an image analyzer. The crack evolution was evaluated using three fractal dimensions. The first, D_s, measured the level of cracking and crack interconnectivity in the sample. The second, D_d, measured the size distribution of the clay fragments during the drying induced fragmentation of the clay. And the third one, D_b, measured the degree of roughness of the clay fragments’ outlines. The D_s ranged in values between 0.869 and 1.532, with the values of D_s increasing as the level of cracking increased in the sample. D_d and D_b were equal to 3.61 and 1.107, respectively. These two fractal dimensions were measured in the sample after the desiccation process was complete. The application of the resulting desiccation process of the clay sample to the design waste containment systems is also presented.

Fabric in granular materials refers to the arrangement of particles and pore spaces. This study focuses on the changes experienced by the void system in a simulated granular material under direct shear stress condition. Using a plane stress direct shear apparatus, an image analyzer, and the fractal dimension concept from fractal theory, this study shows that the degree of roughness of the pore walls affects not only the unsaturated hydraulic conductivity of the pores but their saturated hydraulic conductivity as well. It was determined that the efficiency by which water is transmitted by the voids depends upon the degree of roughness of the pore walls. The degree of roughness of the pore walls was evaluated using the fractal dimension of the profiles of the pores.

The influence of temperature on soil engineering properties is a major concern in the design of engineering systems such as radioactive waste disposal barriers, ground source heat pump systems and pavement structures. In particular, moisture redistribution under pavement systems might lead to changes in unbound material stiffness that will affect pavement performance. Accurate measurement of thermal effects on unsaturated soil hydraulic properties may lead to reduction in design and construction costs. This paper presents preliminary results of an experimental study aimed at determining the effect of temperature on the soil water characteristic curve (SWCC) and the unsaturated hydraulic conductivity function (k_unsat). Pressure plate devices with volume change control were used to determine the SWCC and the instantaneous profile method was used to measure k_unsat. These properties were obtained for two fine-grained materials subjected to controlled temperatures of 5°C, 25°C and 40°C. The results were used to perform a sensitivity analysis of the effect of temperature changes on the prediction of moisture movement under a covered area. The findings were compared to field measured water content data obtained on the subgrade of FAA William Hughes test facility located in Atlantic City. Results indicated that temperature affected the unsaturated hydraulic properties of the two fine-grained materials used in the study. For the DuPont soil, the water retention at 5°C was higher than that for higher temperatures for suction levels lower than about 10,000 kPa; while the k_unsat functions were not statistically different. The County soil holds around 10% more moisture at 5°C than at 40°C for suction levels higher than about 1,000 kPa and the k_unsat function at 40°C was slightly higher than the function at 5°C. The finding from sensitivity analysis showed that the most accurate modeling was the modeling with unsaturated material properties at 40°C and the difference in unsaturated hydraulic properties did lead to some variations in modeling results.

Rainfall has been considered as one among the major causes of shallow slope failures. Infiltration of rainwater increases pore water pressure, changes degree of saturation and causes the loss of strength in soil, which all attribute to the reduced factor of safety of the slope. A series of physical model tests were conducted on slopes prepared at different soil void ratios and steepness. The slopes were subjected to three different rainfall intensities – 0.28 mm/min, and 0.55 mm/min until the soil reached saturation and time-wise variation in seepage velocity, spatial variation of soil suction, and soil deformation were measured. The study results showed that pore water pressure and the velocity of movement of wetting front increase with an increase in void ratio, and increase in the intensity of rainfall. Deformation analysis results of the slope materials were performed with the measured location of wetting front and soil suction for different time period and matched well with the experimental results. This study was useful to quantify the effect of void ratio, and intensity and duration of rainfall on slope.

Construction of large highways often involves raising the elevation of existing ground to build the planned highway subgrade. As a result, borrow materials are typically placed to form embankments with different heights and slope inclinations. Often times factors such as different embankment heights, different slope inclinations, and variable subsurface conditions in long highway alignments can make the selection of the most critical cross sections in terms of slope stability analysis a tedious task. As an example, the cross section with the largest embankment height may not be the most critical case to analyze if it is proposed to be founded on a very dense subsurface soil. To identify the cross sections prone to potential global slope stability failures when designing embankments, a soil strength parametric study was performed for different embankment heights in drained and undrained conditions. The results of the analyses and parametric study were used to determine the critical condition and develop equations and tables correlating the minimum allowable shear strength of the soil to the height of the proposed embankment. The suggested equations and tables are useful tools to predict the sections with potential failure along highway alignments in the preliminary slope stability analysis process. The equations are compatible to both allowable strength design (ASD) and load resistance factor design (LRFD) slope stability analyses.

Reinforced concrete (RC) structures are exposed to a variety of environmental stressors that may initiate the deterioration of structures. The system deterioration, however, must be considered as a stochastic process since the progress of deterioration varies widely with several uncertain factors, which are generally not captured by available data. Considering that maintenance strategies are planned based on the estimates of the extent of structural deterioration, a systematic effort is needed to incorporate various sources of uncertainty in predictive models and decision-making algorithms. To this end, the current study utilizes Weibull distribution to investigate the deterioration of RC bridges. In the developed models, a set of condition states is used to describe the level of structural degradation characterized by different performance rates, ranging from perfect functioning to complete failure. Furthermore, a range of maintenance actions are examined depending on the expected damage state. By taking into account the factor of cost, the developed probabilistic framework directly contributes to improve the current maintenance policies through the identification of the most optimized preventive or corrective actions while the safety of the structure is ensured.

Installation of buckling-restrained braces (BRBs) is an effective means to improve the seismic performance of building structures. The authors have developed a new variation of BRBs that use steel-and-mortar planks for the buckling-restraining system. A large number of laboratory test results, suggest that these BRBs exhibit excellent performance on par with widely used commercialized BRB products. Using the new BRBs, an experimental study was conducted to examine how bending deformation of the steel core affects the cyclic loading performance of the BRB. Four BRB specimens were fabricated in the laboratory. The specimens combined a flat-plate steel core with a relatively small width-to-thickness ratio of six, and a very stiff buckling-restraining system whose Euler buckling load was six times the yield strength of the steel core. Two specimens placed longitudinal round bars in the mortar-free gaps adjacent to the side of steel core. Two specimens kept the gaps empty by intension. The test results suggest that placement of round bars in the mortar-free gaps is an effective method to control major-axis bending deformation of the steel core.

This paper presents the experimental investigation of an innovative energy dissipation system in steel moment resisting frames. In the proposed system, a replaceable beam with a smaller cross-section than that of the main beam is placed at the mid span of the beam designed to act as a shear fuse. This shifts the location of the plastic hinging from the end of the beam to the middle since the shear fuse yields in shear prior to the flexural yielding of the main beam. This system eliminates the need to comply with the rigorous limitation on the beam span-to-depth ratio that is proposed by seismic design codes to ensure the formation of plastic hinges at the two ends of the beam. Moreover, this system enjoys an increase in the amount of dissipated seismic energy and a more stable hysteresis behavior. Finally, the system increases the resilience of the building as the shear fuse is readily replaceable after an earthquake.

This study describes the development and implementation of a geotechnical engineering software package within the statistical language and environment R. The software package, aptly named geotech, has the capability to perform a range of geotechnical engineering computations, and represents an additional option in the geotechnical engineer’s toolbox. R is an object-oriented language and environment for statistical computing that is gaining popularity in science and engineering. In addition to the development and features of the software package, this study also describes its implementation in a junior-level introductory course in geotechnical engineering at Merrimack College in North Andover, Massachusetts. In the current version of the software package, an emphasis has been placed on calculations that arise within the context of an introductory geotechnical engineering course. The contribution of this project is an open-source, freely available software package for broad usage in geotechnical engineering education, research, and practice. A similar framework could be followed for the development of R packages for other areas of civil engineering practice.

In the current practice of bridge engineering, structures are designed and evaluated using static loads. In order to account for the dynamic nature of the true loading condition, static vehicle loads are increased by a dynamic amplification factor (DAF). The DAF has been widely studied for conventional bridges and has been found to be a function of vehicle forcing frequency and the fundamental frequency of the bridge. As a simplification, many design codes determine the DAF factor based on common bridge characteristics, namely the span length. The AASHTO LRFD Bridge Design Specifications simply use a single, conservative value for conventional bridge types. In the case of buried bridge structures, the dynamic behavior is complicated by the soil layer present between the asphalt and structure. In order to accurately determine the response of buried box culverts in a dynamic loading scenario, the interaction between the asphalt, soil, and structure must be taken into account. Through a parametric finite element analysis, four aspects of the asphalt-soil-structure system are examined in order to determine the factors which most influence its dynamic response. Parameters under scrutiny are depth of fill, fill stiffness, culvert span length, and culvert flexural rigidity. This research shows that fill depth and slab thickness are most influential in determining the dynamic amplification factor. However, span length and soil stiffness do have some effect.

To evaluate the required resistance factor for geotechnical foundation design, an approach was developed to evaluate the annual probability of failure and to calibrate the required deterministic safety factors. The paper describes the approach and presents the calibrated load and resistance factors corresponding to an annual probability of failure of 10^-4 for three jacket structures offshore Norway and the U.K. The results of generic calculations of load and resistance factors are also presented. These compared well with the calibrated load and resistance factors obtained for the three “real-life” jackets. The calibration of the load and resistance factors requires the evaluation of the model uncertainty for each pile design method and the statistics of the uncertain parameters in the analyses. The results show that the annual probability of failure varies significantly with pile design method. The annual probability of failure depended strongly on the uncertainty in the geotechnical calculation model. Suggestions for improvements to the methodology and to the codes are made, including how to define and improve the evaluation of the model uncertainty.

Steel-plate composite (SC) walls consist of a plain concrete wall reinforced with steel plates on the two (interior and exterior) surfaces. The steel faceplates are anchored to the concrete infill using steel headed stud anchors that are welded to the inside surfaces of the steel faceplates and embedded in the concrete. Additionally, the steel faceplates are connected to each other using tie bars that are also embedded in the concrete infill. These tie bars brace the steel faceplates during concrete casting, and act as transverse reinforcement for the finished SC walls. SC walls facilitate modular construction options where the steel modules can be fabricated in shops or factories, assembled on site, and then filled with concrete. Modular construction approaches can improve construction schedule and thus economy. SC walls are being used in the third generation of nuclear power plants being built in the U.S. and China. They are being considered for small modular reactors (SMRs) of the future, and for multi-story commercial structures as part of the core structure providing lateral stiffness and strength. The design of SC walls for nuclear facilities is governed by AISC N690s1 (2015) and for commercial buildings by AISC 341-17 (upcoming). These specifications include prescriptive provisions for the design of SC walls, but only performance-based provisions for the anchorage of the SC walls to the concrete basemat or foundation. Two performance options are permitted for the anchorage of SC walls to the concrete basemat: (i) where the anchorage is designed to be stronger than the SC walls, and (ii) where the anchorage is designed for 200% of the calculated seismic demand + 100% of other demands. This paper discusses two anchorage options for SC walls: (i) with welded rebar anchors designed to be 25% stronger than the SC walls, and (ii) with embedded dowel bars designed with 200% overstrength with respect to the calculated seismic demands. Both these anchorage options have been considered and built for SC wall designs in the U.S. and China. The first option that anchors the full strength of SC walls is preferred for commercial buildings where ductility is a significant performance requirement. Both the full strength and the overstrength anchorage option can be used for SC walls of nuclear facilities where strength with respect to calculated design demands is a significant performance requirement. The paper discusses the experimental behaviour, analysis models, and design and detailing recommendations for both these anchorage options. The focus is on the cyclic lateral load-deformation responses and failure modes of SC walls anchored to the concrete basemat using these options. The paper also discusses the advantages and limitations of both these anchorage options from construction ease, schedule and economy perspectives.

The near-surface-mounted (NSM) strengthening method is a relatively new method for rehabilitation of reinforced concrete structures and can overcome some of the disadvantages of the other strengthening systems. In NSM method, longitudinal grooves are first cut into the concrete cover of an RC member, then reinforcing bars or strips, are inserted in these grooves and bonded with an epoxy paste or cementitious material. Although the NSM reinforcement can preclude delamination-type failure, one of the main factors that affect the efficiency of the NSM method is still the bond between the NSM reinforcement and the concrete. Shape memory alloys (SMA) are a class of metallic alloys that can remember their original shape upon being deformed. Besides their ability to recover large strains with minimal residual deformations, SMAs possess excellent corrosion resistance, good energy dissipation capacity, and high fatigue properties. This study investigates bond characteristics and load transfer mechanisms between NSM SMA reinforcement and concrete. A modified pullout test set-up that consists of a C-shaped concrete block, where the NSM reinforcement are placed at the center of gravity of the block, are used for experimental investigations. The effects of various parameters such as NSM reinforcement type, embedment length, type of epoxy on the bond behavior are studied. The slip of the SMA reinforcement relative to concrete is measured using DIC method at the loaded and free ends of the specimen and the bond-slip curves are developed.

A sustainability comparison was performed for two design alternatives considered for the replacement of an existing culvert bridge southeast of Dupuyer, MT. The first alternative supported the bridge on deep foundation elements and the second alternative employed a geosynthetic reinforced soil integrated bridge system (GRS-IBS). The sustainability comparison focuses primarily on the predicted embodied energy and carbon dioxide emissions for each alternative. Construction costs and some social aspects are also considered. The embodied energy and carbon dioxide emissions estimates were made using the streamlined energy and emissions assessment model, which is a streamlined life cycle analysis methodology specific to geotechnical works. Based on the available data and our assumptions, there is little difference in the embodied energy between alternatives. However, the GRS-IBS alternative resulted in lower carbon dioxide emissions and lower construction costs, suggesting it is more sustainable than the structure supported by deep foundation elements. A sensitivity study suggests these findings are reasonable for the assumptions made in the analyses. One limitation to this study is the uncertainty in the long term performance and reliability of GRS abutment systems compared to that of traditional pile supported structures.

This paper will discuss some benchmark, well documented extreme cases relating to earthquakes, fires, hurricanes, winds, floods, and terrorist attacks, and the impact they have had in modifying design standards. The authors will share their experience with responding to events including 9-11, Hurricane Sandy, and recent earthquakes that steered their focus on observing resilient structural performance, instead of failures, as is usually done. The new generation of design standards will incorporate performance targets as they relate to multi-hazard exposure, associated risks, and life cycle parameters. To this end, observation of successful cases despite them experiencing loads higher than their design is invaluable. The complexity of learning from the past and predicting and designing for the next extreme hazard, with its often counter-active character of other associated multi-hazards, in an overall resilience framework will be discussed.

High capacity of rock-socketed or end bearing drilled shafts is often not fully exploited due to the highly conservative design that many local codes and local practices around United States dictate. This reduces the cost efficiency of drilled shafts versus other foundation solutions. ADSC is interested in developing a test program procedure that will be economically feasible for engineers and foundation contractors to perform in every project even when load tests are not specified. Static load tests (including conventional top-down and bi-directional load tests) are invaluable but often prohibitive due to high cost and time constraints. Alternatively, high strain dynamic testing of drilled shafts has increased significantly in recent years with well-established testing procedures and analyses. More specifically, ADSC is considering using dynamic load testing to prove the high capacities of drilled shafts in several rock formations around the country and establish limits of extrapolation to larger diameter shafts from tests on smaller diameter shafts. The purpose of this paper is to present the theoretical basis of ADSC’s technical endeavor. More specifically the paper will focus into 2 different topics; i) parameters affecting drilled shaft performance and ii) the theory and principals of dynamic testing as applied to rock socketed drilled shafts, as well as, case studies of dynamic tests in rock socketed drilled shafts.

Two buildings that suffered significant differential settlements from the action of hydro-compressive soils in western Colorado are reviewed. The buildings are located on a relatively large alluvial fan. Alluvial fan deposits are known to collapse when wetted in the arid climate common to western Colorado. The subsurface soils were explored for zoning, building design and after settlements became an issue. It was necessary to characterize the change in conditions to prepare remedial recommendations. Comparisons of pre and post-construction conditions were used to estimate future performance. Field penetration tests, moisture and density determinations, percent saturation, one dimensional consolidation and classification tests were used to judge future performance. Prediction of advance of the wetted front is both critical and difficult to estimate. Graphs of the moisture versus depth are presented over the period 2000 to 2010. Suggested remedial measures are included. Actual design and implementation of the remedial measures is described in companion papers.

A group of detached single family houses founded on shallow footings on hydro-compressible soils suffered differential settlements up to 46 cm (18 inches). Some adjacent houses suffered no discernable damage. Most of the houses had box-like foundation wall structures with no interior or isolated footings. The foundation walls were well reinforced and surprisingly undamaged, but the wood superstructures of some of the houses were damaged beyond economical repair. Some of the houses had previously undergone remedial repairs with mixed success. The nature of most of the damage was economic (serviceability concerns), although some safety issues did exist. The time rate of settlement and geotechnical predictions for future movement combined with the nature of the damage to define the objectives for design of the remediation. That design depended on a complex interplay of geotechnical, structural, drainage, and construction engineering. Several schemes were considered for the remediation including underpinning and soil stabilization. Underpinning schemes studied included push-piles, helical piers, drilled micro-piers, and large diameter drilled piers with new grade beams. All underpinning schemes were designed to resist future downdrag from the continuing consolidation of the underlying soil. The soil loses much of its strength and stiffness when wetted, thereby reducing the lateral support to the small diameter piers. This meant that buckling of underpinning solutions had to be considered. Conventional rules of thumb for driven piling were not directly applied to the small diameter piles and piers. Instead second order analyses were performed using upper and lower bounding assumptions for stiffness of the soil. Soil densification by compaction grouting was also studied, and was the best engineering choice at some sites.

Two masonry buildings founded on shallow footings on collapsible soil suffered significant distress from settlement. Both buildings are of similar design and both serve to house and maintain heavy vehicles as well as office areas. Both buildings suffered differential settlement on the order of eight to nine inches, with severe damage to masonry walls. Remediation schemes considered included foundation underpinning by micro-piers, push-piles, raft foundation, compaction grouting, and soil stabilization under slabs. The pros and cons of each scheme are discussed and the reasons for the decision to utilize compaction grouting as the preferred solution for the masonry buildings are presented. Although the building sites are adjacent, the depths of collapsible soil varied dramatically owing to the geology of the debris fan upon which the buildings were founded. The owners of the two buildings had differing resources available to cover the costs, thus the scope of repair was more extensive at one of the buildings. The structural approach was to design for both soil densification and spot underpinning. The soil densification was to improve spread footing performance. The specification of discrete locations for the grout columns themselves allowed rational distribution of reactions and effects in the existing foundation elements. Water ingress was the catalyst that triggered soil collapse but the water issues were unique to each site. Unusual and extensive measures to alleviate water ingress for each building are discussed. Repairs to the masonry bearing walls, some of which were severely damaged, are presented.

Two masonry buildings in the Glenwood Springs area of Colorado had undergone significant differential settlement following their construction. The foundations consisted of spread footings and slab-on-grade. Compaction grouting was chosen as the remediation technique of choice to treat the collapsible soils beneath the two structures. Compaction grouting involves the injection of low-slump, stiff, low mobility grout to displace and densify the subsurface soils. Compaction grouting was performed at depths up to 100 ft below the structures. Since treatment of the subsurface soils via compaction grouting, there has been no further signs of distress or differential settlement in the buildings.

The 740ft Swing Bridge in Katharyn, KY was originally constructed in 1905 with a 338ft center-pinned swing truss carrying a single track. The swing truss was fixed in place in the 1940’s. The bridge was selected for replacement due to significant deterioration of the bridge, the pin connections, and the members. The selected alternate was four deck-girder spans, which adds two concrete piers in the Salt River waterway. While attempting to install the northern pier pile foundation, a debris field consisting of stones, concrete, and other materials was discovered. After evaluating the results of a preliminary investigation and excavation, it is believed that the original pivot pier had collapsed during a flood event shortly after construction and was abandoned to the river. A new pier was then simply built on top of the remains. A reassessment of the alternates and additional geotechnical exploration indicated that the traditional pile foundation should be replaced with a micro-pile system that penetrates the debris field. Thus, the original pier location and superstructure layout were maintained. The presentation includes a project overview and then focusses on the debris field discovery, the foundation redesign including impacts of obstructions, and final construction of the bridge. All analysis and design were completed according to the current applicable edition of the American Railway Engineering and Maintenance-of-Way Association, Chapters 8 - Concrete Structures, and Chapter 15 - Steel Structures.

The movable bridge crossing the Cumberland River in Nashville, TN has an overall length of 695ft with a center swing span that is 275ft out-to-out. Two fixed-position spans on each side of the swing span are 206ft from center-to-center of bearings. It was found that during routine operations the swing span would not completely close. Inspections noted that the adjacent ‘fixed’ span had started moving toward the swing span and creating points of interference. Additionally, it was concluded that the reason for the encroachment was deterioration of the pier’s core caused by scour. Since the location is subject to both heavy river and heavy rail traffic, there is effectively no downtime for the structure. Thus, all construction work was required to be performed within two 12-hour outages. Included herein are an overview of the bridge history, the sources of the span movement, the pier repairs, and the integrated geotechnical and structural collaboration used to reposition the span.

The Colton Crossing Design Team developed an innovative approach for grade separating the Union Pacific-BNSF quadruple diamond at-grade crossing at Colton, California. The site lies in a developed area bounded by Interstate 10 on the north and residential/commercial neighborhoods on the south. Due to the need to maintain operations on existing tracks during construction and close proximity to I-10, traditional soil embankment fill with side slopes was not feasible for most of the project limits. Since the grade separation required retaining walls as high as 40 feet to elevate UP tracks over BNSF, high bearing pressures and expensive retaining walls were expected. The retaining walls and fill were estimated to be about 40% of the total cost of the project. In addition, Colton lies within an active seismic zone and the nearby San Jacinto fault has the capability of producing very large ground motions in an earthquake. The weight of concrete retaining walls and soil fill would result in large inertial forces, high peak bearing stresses and the potential for catastrophic failure of the walls and foundation soils in a seismic event. A novel approach to the retaining walls and fill was developed by the design team which proposed the use of lightweight cellular concrete fill with precast concrete panel fascia walls to form a cellular concrete retaining structure. The design team developed design criteria since no AREMA or AASHTO guidance was available for this type of structure. The design team performed advanced service and seismic design utilizing finite element analyses as well as other traditional methods. The analyses verified that the expected performance and construction costs were reduced considerably. This innovative cellular concrete retaining structure has the following advantages: (1) lighter weight and stronger than compacted soil backfill; (2) built using small equipment and without importing a large volume of fill, thereby reducing impacts to the environment; (3) no lateral earth pressures and very small live load surcharge pressures on bridge abutments and side facing walls; (4) reduced seismic inertial effects due to the reduction in mass, as well as enhanced seismic stability due to the large block-like behavior of the retaining structure; (5) greatly reduced anticipated settlements, especially in combination with shallow ground improvement; and (6) cost savings of up to 30% compared to conventional cast-in-place concrete walls with tie rods and soil fill.

Using design elements and lessons learned from the UP-BNSF Colton Crossing Project in Colton, California, the Merchants Bridge Design Team adapted an innovative approach for the Merchants Bridge West Approach reconstruction of the Terminal Railroad Association (TRRA) track in St. Louis, Missouri. The existing west approach consists of an open deck steel trestle supported on steel frame bents. The project begins at existing Bent W6 which was part of a previous partial reconstruction of the Merchants Bridge over Mississippi River in 2005 and extends westerly to the existing concrete abutments. Due to TRRA’s requirement that rail operations be maintained during construction, the existing bridge was fully encapsulated within the lightweight concrete (LCC) embankment. Conventional MSE wall panels were selected to contain the LCC. Auger-cast piles placed underneath the MSE wall panel footings increased the bearing capacity where it exceeded the allowable bearing capacity of the soil. Another issue arose because the project site is located near known active New Madrid and Wabash Valley seismic zones. Liquefaction potential of the existing fine alluvium soil found at the project site was a particular concern. In addition, several existing utilities were present under the footprint of the proposed embankment. Utility bridges were proposed to minimize the impacts on the utilities but construction constraints challenged placement and methods of installation. The design team performed advanced service and seismic load design utilizing finite element numerical analyses as well as other traditional methods. “Hard points” were identified within the embankment and analyzed for increased stresses within the LCC embankment. A reinforced rock mat was used to distribute the load of the embankment to the auger-cast piles to help reduce differential settlement. Liquefaction potential and seismic design was analyzed using the AREMA Level 1, 2, and 3 earthquake event criteria. To fully understand the utility “bridge” concept, many methods were considered and analyzed to estimate the settlement of each utility impacted by the placement of the new LCC embankment fill. The design for Merchants Bridge West Approach Reconstruction has the following advantages. (1) Track operations could be maintained throughout construction. (2) Cellular concrete is lighter and stronger than compacted soil backfill, increasing stability and decreasing settlement impacts. (3) Increased seismic stability due to the embankment behaving like a large block that moves uniformly. (4) Utility bridge solutions work with limited overhead clearance under the existing tracks.

A combined pile raft foundation (CPRF) is a type of foundation which has the advantages of both shallow foundations (e.g., mat foundations) and deep foundations (e.g., pile foundations). The CPRF includes piles, raft (mat), subsoil and, occasionally, a cushion. Unlike traditional foundations, where the load is supported either by the piles or rafts (mats), the CPRF considers the piles and raft to share the load along with the subsoil. The CPRF mostly requires piles to decrease the settlements of structures, therefore improve the performance of the soil in providing foundation support. A load-transfer cushion is occasionally included at the interface between the piles and the mat to help the rigid pile elements and the subsoil to work together. The CPRF system has been used throughout the world for several years to support tall buildings. The ideal soil profile for the CPRF is a combination of stiff clay and dense sand. The CPRF support system is studied for this paper for use in supporting heavy dynamic equipment. Such an installation imposes large dead load and dynamic load requirements on the subgrade soil and has stringent settlement requirements for daily operation. This installation is further complicated by the less-than-optimum sites which are common for industrial construction. Since the dynamic characteristics and shear capacity of pure pile installations are limited, the combination of a mat with piles should be considered in order to provide the needed load support and stiffness. In this study, the heavy dynamic equipment under consideration is a steam gas turbine (STG). An STG requires a large, thick concrete table-top, columns and a mat. The settlement and dynamic induced movements during operation are much more severe than typical high-rise buildings. Aside from the settlement improvement of CPRF typical for high-rise buildings, the heavy dynamic equipment performance can be substantially improved if the subsoil is considered in the design, as compared with a design which has only a pure pile cap foundation. The use of partial piling in the foundation provides soil improvement to increase dynamic load capacity and performance improvement. Modeling of the complex soil-structure interaction is required for a reliable design. In this paper, SAP2000 is used to model the dynamic performance of the foundation considering both operating static and design seismic loads. Soil conditions are included and modeled as properties of links in SAP2000 to search for the most favorable characteristics. Where appropriate, the results are checked for strain capability with the soil through a simple, iterative process. This paper also considers a soil improvement method which uses vertical reinforcement (such as drilled or driven piles with no connection to the foundation mat at the top) as rigid inclusions and transfer of mat loads to the deep foundation. The dynamic soil interaction analysis required for a CPRF foundation is often ignored by geotechnical consultants as a soil improvement option because it requires significant structural engineering input. The analysis presented here can help to understand the dynamic soil-structure interactions to determine a more realistic result.

Depending on soil conditions, high-rise structures are commonly designed either on piles or spread footings. However, design solutions including both spread footings and piles are typically rejected given the potential for unacceptable differential settlements between the columns/shear walls supported on piles and the columns supported on spread footings. Further the potential contribution of the pile cap as a footing is commonly not considered. A design solution considering the foundations as part of a very flexible mat on piles allows the engineer to consider the pile caps as footings capable of developing soil pressure and the piles as settlement reducing elements working at 70 to 80 percent of their axial capacity. The analysis provides total deformations under footings, pile caps, and individual pile loads under all the load combinations required by code. The three-dimensional model developed for the mat-on-pile analysis allows performance of a sensitivity analysis of the expected range of soil properties. As a result, the geotechnical engineer can provide soil spring constants for footings and for the piles in tension and compression, as well as the allowable soil pressure that the analysis indicates will result in acceptable differential settlements. These parameters are the input required in commonly used structural engineering software used to determine the structural solution. The structural solution using these parameters will substantially agree with the geotechnical analysis and will provide significant savings in foundation cost. The method is illustrated on a 24-story structure. The analysis is supported by a geotechnical investigation and a pile load test that has been completed for the building.

This paper will describe the approach that many state DOTs have taken to develop proactive statewide scour programs to assess, prioritize and protect all types of over-water bridges. FHWA compliance requires that a plan of action be implemented if a bridge is coded/rated scour critical. When this occurs, bridge owners are often required to implement a short term flood monitoring program until protective more permanent scour stabilization alternatives can be designed and installed. Scour awareness has increased over the past 25 years and FHWA design standards for new bridges have been updated and revised; however, predicting future scour at existing bridges remains challenging and requires engineering judgment. Bridges owners do remain skeptical of the need to install effective countermeasures when their 75 year old bridge shows no observed signs of scour and the bridge has withstood multiple flood events. Scour is the number 1 cause of bridge failures in the United States and experience is needed to recognize a truly vulnerable bridge and protect it from damage.

Large quantities of industrial wastes are being generated worldwide due to rapid urbanization and industrialization. In India, aggregate crusher units produce enormous quantities of stone dust, a by-product produced during crushing of stone. Stacking or disposal of such large quantities of stone dust in open areas is not an environment friendly solution. Utilization of this by product in civil engineering applications is likely to provide an acceptable solution. Efforts are underway to utilize stone dust in civil engineering construction industries so that minimizing the threat caused to environment in the direction of sustainable development. In this direction, present paper pertain the results of the compressive strength experimental study carried out on material prepared using stone dust and expanded polystyrene(EPS) beads. The experiments were conducted by adding EPS beads with different mix proportions with respect to the weight of stone dust. The mix ratio percentages used in the present study are 0.033, 0.066, 0.099, 0.132, and 0.165. Density of EPS beads used in the study is 16 kg/m³. Cubical specimen of size 70 mm × 70 mm × 70 mm was used for evaluating the compressive strength of material for curing periods of 7 and 14 days. The results indicate that the compressive strength, density and stress-stress pattern of the prepared material was significantly influenced by the curing period and mix ratios. For a particular mix ratio value, compressive strength of material increased with increasing curing period and for a particular curing period value it decreased with increasing mix ratios. The density of the material is decreased with increasing mix ratio values. The relationship between stress and strain was observed to be nonlinear.

The objective of the testing program, approved by the EPA was to evaluate the performance of grouting materials used in the rehabilitation of cracked concrete structures, including pipes, to quantify the infiltration using a combination of model and laboratory tests at the Center for Innovative Grouting Materials and Technology (CIGMAT). A combination of grout and grout-substrate bonding with a simulated model test are being used to evaluate grouts for leak control at repaired cracks in concrete. The concrete crack repairs were simulated using concrete rings placed at selected distance apart and the grouted cracks were tested to 34 kPa (5 psi) water pressure, after subjecting the repaired joints to wet-dry cycles, to quantify the effective reduction in water infiltration. In this study, a commercially available epoxy grout was investigated based on a test protocol developed for EPA to evaluate the performance of grouts to control leak in cracked concrete. The average compressive strength, failure stain, and initial modulus after 3 days of curing were 45 MPa, 8%, and 1.5 GPa, respectively. After 6 months of wet-dry cycle test, the average bonding strength was 1.6 MPa. Model tests showed that the epoxy grout investigated in this study was effective in eliminating the leak in the cracked concrete immediately after grouting and after two wet and dry cycles over period of one month.

Cement and polymer grouts are being used in various construction and rehabilitation applications related to oil wells, piles, structures, leaking pipelines and ground improvement. In this study oil well cement (Class H), Portland cement (Type 1) and poly acrylamide were used as representative cement and polymer grouts. The smart cement and smart polymer grouts were developed using conductive fillers to make them piezoresistive materials. The highly sensing properties of the smart grouts will help with the real-time monitoring of the performance of the grouts from the time of installation to the entire service life. A series of experiments were conducted to evaluate the smart grout behavior with and without 1% nano silica (NS) and 0.5% biosurfactant (BS) to determine the sensitivity in terms of piezoresistivity. The Marsh Funnel flow time and the viscosity increased by addition of NS and BS for both types of grouts. Addition of 1% NS improved the compressive strength and piezoresistivity of both smart cement grouts. For the smart oil well cement grout the piezoresistivity at compressive peak stress varied from 155 to 179% and it increased to 209-237% with 1% nano-silica. With 1% nano-silica and 0.5% biosurfactant the piezoresistivity reduced to 64 to70%. For the Portland cement grout with with 1% NS and 0.5% BS the piezoresistivity varied from 124% to 178%. For the acrylamide grout the resistivity changed by 25% at a compressive stress of 100 kPa and the addition of nano silica and biosurfactant reduced the peiezoresistivity of the grout. A nonlinear piezoresistive model predicated the compressive stress–change in resistivity relationship of the smart cement grouts with and without NS and BS very well.

Output-only system identification methods assist engineers in determining operational modal properties of constructed structural systems. Sensors and data acquisition systems have a finite reliability; even state-of-the-art technologies are susceptible to missing packets, erroneous values, and other malfunctions. It is expected that missing data points degrade the estimation accuracy of important structural features such as natural vibration properties or damage metrics. The goal of this paper is to quantify corresponding structural information losses in modal identification. The main hypothesis of this paper is that despite missing data points caused by measurement issues, there is a substantial amount of structural information hidden within the observed data. Structural modal properties can be estimated with sufficient accuracy even with significant data loss through the use of the STRIDE algorithm. This study investigates the response of a three-story steel frame captured by a network of accelerometers. Systematic sensor failures are implemented artificially to study their effect on modal property estimation. It is shown that structural mode shapes can be computed with a certain accuracy even when 90% of the measurements for a particular story are lost.

Temperature-based (TB) model updating has been researched as a novel approach to inform numerical models of constructed systems. The overall TB concept utilizes temperature variations as a measureable forcing function for bridges and thus can be used to obtain a complete input-output relationship (or transfer function). This is achieved through instrumentation of both the critical members and movement mechanisms. Studies were conducted on existing bridges where the temperature (input) was measured at select locations along with the corresponding strains, displacements, and rotations (output). Then TB model updating was performed to refine a numerical model according to the measured input-output relationship so it more closely represented the actual behavior of the structural system. This paper discusses the approach for TB model updating along with the primary benefits and drawback of the methodology.

In what is becoming more and more common occurrence in the Eastern Coal Fields, a site that has been targeted for redevelopment is found to be covered with as much as 60 to 70 feet of uncontrolled mine spoil fills, placed at the conclusion of strip mining activities conducted during the past century. As such, they require deep foundations or a significant ground improvement effort to allow for shallow foundations to support vertical construction at the site. Today, many of these areas are being reused as part of infrastructure and site development associated with the shale gas industry. The use of dynamic compaction to improve mine spoils can provide an economic form of ground improvement, provided the magnitude of loading proposed at a site is reasonably moderate, and modest bearing pressures are required. Dynamic compaction has become an increasingly viable and attractive ground improvement option for mine spoil sites, given the ease of implementation and degree of effectiveness over a wide variety of ground conditions. Based on the 80 case studies reviewed as part of this study, dynamic compaction was found to be highly effective at improving sites with low-rise structures, and where measured, increased SPT N-values in the upper 30 feet of mine spoil materials up to 40% on average.

Design of geothermal energy piles requires consideration of the complex interaction between temperature change in the pile and induced stresses and deformations in the pile and soil, which may affect building’s performance. Hence, it is of utmost importance to understand and quantify the load transfer mechanism of energy piles under thermal and mechanical loads through rigorous numerical analysis. Thermo-mechanical response of geothermal energy piles in sand has been investigated in the present work using axisymmetric nonlinear finite element analysis procedure. Herein, the stress-strain response of piles is considered to be linear-elastic. The stress-strain response of sand has been simulated using state parameter based constitutive model CASM. Floating and end bearing geothermal energy piles of different lengths and diameters in sand have been analyzed under mechanical and thermo-mechanical loading for studying the displacements of pile and the axial stresses in pile. It is observed from the results that the relative displacement between pile and soil depends on the applied thermal load on the pile, the relative density of the sand and the end condition of the pile. Also, the piles exhibit higher axial stresses under thermo-mechanical loading as compared to that under mechanical loading.

Microbially induced calcite precipitation (MICP) is one of the most promising emerging environmentally conscious soil improvement techniques. The bio-cementation process offers an alternative to traditional mechanical, Portland cement, and silicate based ground improvement methods, by utilizing microbial activity to induce calcite precipitation on soil particle surfaces and at particle contacts. Despite extensive demonstration of the process at the laboratory-scale, few large and field-scale applications have been completed to demonstrate and understand the biogeochemical process at the meter scale. An instrumented large-scale bio-cementation test was performed using a 1.7-meter diameter tank containing 0.7 m³ of a poorly-graded natural sand, and treated with three wells positioned in a triangular pattern at a well-to-well spacing of 1.2 m. Eight non-uniform cementation treatment injections were completed to determine the extent to which the improvement level could be spatially controlled, and to establish a cementation gradient for study of improvement across a broad range of cementation levels. Prior to treatment, miniature cone penetrometer soundings were used to assess pre-treatment conditions. During treatment, tank specimens were monitored spatially for shear wave velocity changes. Following treatment, cone penetration soundings were performed to assess improvement spatially, and discrete soil samples were obtained for calcite content measurements. Post-treatment measurements indicated that a gradient of cementation was achieved, with highly cemented locations reaching shear wave velocities near 970 m/s, calcite contents in excess of 5.0%, and increases in penetration resistances near 545%.

For vacuum-assisted ground improvement on highly compressible alluvial or marine deposits, the application of suction pressure accelerates consolidation and controls lateral deformation by isotropically increasing the effective stress. Analytical, numerical, and experimental research on vacuum-assisted prefabricated vertical drains (PVDs) has been conducted at University of Wollongong in past 15 years. Key factors such as vacuum distribution, extent of smear, occurrence of non-Darcian flow, and large-strain effects have been studied and their implications are presented in the paper. Some practical approaches have been proposed to facilitate industrial design schemes for vacuum consolidation. 2D plane strain conversion approach has been proposed for numerical modeling of large soft area treated with multiple PVDs. The behavior of vacuum stabilized soil in the field has been predicted by the numerical models applied to selected case studies through fully-instrumented field trials, by measuring settlement, lateral movement and excess pore water pressure data. A good agreement between the predicted and field data was achieved. Some key theoretical and numerical approaches are presented in this paper, together with the case study involving the Ballina Bypass in Australia.

The paper describes the use of jet grouting technology, as a soil improvement technique used for the excavation support and the underpinning of a viaduct and stadium foundation to permit the construction of a 32 storey residential/office tower constructed over five levels of below grade parking, in very close proximity to the Georgia Street viaduct. The site is located in the near the Yaletown neighbourhood of downtown Vancouver, in close proximity to a number of buildings and other infrastructure, including Rogers Arena, home of the local NHL Vancouver Canucks hockey team, the Georgia Street Viaduct, an elevated structure that is a main artery for commuter traffic in and out of the downtown core and Griffiths Way and Pacific Boulevard. It is also in close proximity to significant roads that provide access to Rogers Arena and support heavy commuter traffic during the day. The site is approximately triangular in shape and located in area of reclaimed land within the former limits of False Creek, a channel that connects to Burrard Inlet and separates the downtown core from the Point Grey Peninsula. The lands were reclaimed by the placement of fills into the former marine environment. The subsurface conditions generally comprise fills overlying native deposit of post glacial marine and glaciomarine origin, overlying dense glaciated soils. Groundwater levels were inferred at depths of 4 to 5 m below street grades and well above the proposed bottom of excavation, located 16 m below street grades.

Soil disturbance (smear zone) can be created while installing vertical drains, within which changes in horizontal permeability and the compressibility of in-situ soil can be observed. Previous studies on different aspects of soil disturbance due to driving vertical drains are limited, so extensive soil characterisation was carried out while installing drains at Ballina, NSW to obtain a more realistic smear zone. Soil disturbance was evaluated by determining the change in the coefficient of permeability, the water content, and volume compressibility away from the drain. The characteristics of the smear zone were compared to the data available from past literatures and indicated that the radius of the smear zone was about 6.3 times the equivalent mandrel radius, which was larger than that observed in the laboratory using reconstituted specimens.

This paper presents the geotechnical challenges faced and targeted ground improvement adopted during the construction of a gas processing facility in the Pilbara region of Australia. The ground improvement solutions implemented on the project included dynamic replacement, rigid inclusions, stone columns, geogrids and geowebs. The ground improvement technologies are discussed in the following context (i) basis of selection, (ii) design development details, (iii) results of the pre-production/performance testing where available, (iv) performance of constructed infrastructure where available, and (v) lesson’s learned during construction. Additionally, the limited success of a high impact roller as an effective and efficient alternative to conventional sheep foot roller for earthwork compaction is also addressed.

An experimental study using centrifuge physical modeling was performed with the purpose of examining the lateral load behavior of rigid inclusion-supported footings. The lateral load behavior of rigid inclusion-supported footings is currently poorly understood. Uncertainty exists regarding the performance of these systems under lateral loading. The results of the centrifuge tests suggest that one of the main components of a typical rigid inclusion-supported footing system, the load transfer platform, plays an important role in determining the capacity and response of such systems under lateral loading.

For deep underground constructions with groundwater, quick and effective in-situ hydraulic conductivity control is important to dissipate the mega hydraulic pressure which becomes critical to underground structures after construction. Recent permeability control methods (e.g., grouting, membranes, pumping, and drain) have several drawbacks, such as setting time, washout, or installation difficulties. Gellan gum is a microbial induced biopolymer with the capabilities of forming hydrocolloid gels when mixed with heated water and limiting water flow through the gel itself. The focus of this study is to investigate the possible usage of gellan gum biopolymer in soil hydraulic conductivity control at various depths and pore pressure conditions. Hydraulic conductivity of gellan gum treated sands were used for laboratory testing. Various pore water pressure and confinement conditions were simulated via pressurized syringe pump permeability testing device to observer the bio-clogging behavior of gellan gum treated sands under high pressures. In addition, soil hydraulic conductivity variations due to overburden confinement and pore water pressure changes were observed. With its quick setting time and soil enhancing properties, the use of gellan gum biopolymer for soil hydraulic conductivity control shows promising results to become an environmentally-friendly alternative in in-situ grouting purposes.

This paper presents the use of an innovative low cost sensor for monitoring corrosion of steel members embedded in concrete. Corrosion of steel reinforcing bars or steel embedded in concrete structural components is a major concern for structures such as bridges and parking garages. Moisture ingress through the cracks is the primary reason for corrosion of such concrete structures, and the problem is compounded with the use of deicing salt in winter months. The salt and moisture levels significantly affect the conductivity of concrete. A low cost sensor for measuring concrete resistivity (or conductivity) was developed by researchers at West Virginia University. This sensor is very durable and can be embedded in concrete members (beams, columns, etc.) at the time of pouring concrete. The data from the sensor can be used to infer the moisture and chloride ingress during the structure’s service life, and this information is useful in evaluating the potential for corrosion of embedded steel. This paper presents laboratory and field results obtained using the resistivity sensor to demonstrate its usefulness. The paper also highlights the simplicity and ease of use of this sensor. In addition, the paper demonstrates the use of commercially available temperature/humidity sensor which can be used in conjunction with the concrete resistivity sensor. Finally, the field results obtained after installing the sensors during a bridge rehabilitation work in East Lynn, West Virginia, indicate that there is no corrosion activity in the steel pile encased in concrete during the first year following the structural rehabilitation.

Modal parameters are subjected to significant changes not only by damage, but also by environmental conditions. Without quantifying environmental effects, applying vibration-based damage detection techniques may result in false damage identification. Collecting vibration and temperature data continuously have enabled researchers to investigate the correlation between environmental effects and identified modal parameters. Amid different environmental effects, temperature variations have been found to have the biggest impact on vibrational characteristics of bridges. In this paper, the effect of temperature on vibrational characteristics of a continuously monitored bridge, located in Perry, Utah, is presented. This bridge is instrumented with a monitoring system that collects vibration and temperature data at different locations of the bridge every hour. For dimensionality reduction, principle components of temperature measurements were extracted by applying principle component analysis (PCA). Natural frequencies of the structure are identified from ambient vibration data using the natural excitation technique (NExT) along with the Eigen system realization (ERA) algorithm. Variability of identified natural frequencies were investigated based on statistical properties of identified frequencies. A nonlinear ARX model and nonlinear polynomial models were used to find the relationship between the measured temperature and natural frequencies. The nonlinear ARX model showed natural frequencies are dependent to previously measured temperatures. This model was validated by using different sets of available data. These two models were evaluated and compared based on the statistical properties.

Operational modal analysis (OMA) techniques have become very popular in the characterization of dynamic properties of civil engineering structures. This is mainly because of their practical capabilities and implementation economy. For civil engineering applications, OMA aims to identify natural frequencies and the related modal damping and mode shapes of a structure under ambient vibration conditions. Generally, when identifying mode shapes, the number of measurement points is an important factor which is usually restricted by instrumentation limitations. To overcome this limitation, data acquisition in multiple patches with roving sensor setups can be applied. In this case, due to the non-stationary nature of ambient vibration, different parts of identified mode shapes are not scaled and the parts of mode shapes should be properly scaled before assembly. The primary objective of this study is to implement the pre-scaling assembly technique in reference-based stochastic subspace identification (SSI/Ref). This procedure allows the automation of the modal identification process in cases of multiple non-simultaneously measured data and takes advantage of the non-parametric assembly technique while using the SSI method. In order to estimate the effectiveness of the applied technique, a three-span steel bridge structure (I-386 Bridge located in Arlington, TN) is considered as the experimental model. Post-scaling and pre-scaling techniques are applied for the identification of mode shapes and the results are compared. Results of the study show that the applied technique can effectively estimate the modal properties of a structure and can be simply implemented and automated.

Vertical ground motions can have a significant impact on the structures vertical response for several types of nonbuilding structures. Tanks and vessels, hanging structures, and horizontal cantilever systems are some examples. The forthcoming ASCE 7-16 code requirements for vertical response spectrum will now account for nonbuilding structures that are sensitive to vertical ground motions. The code requirements are based on Chapter 23 of 2009 NEHRP Provisions, except that the response spectrum will be defined at the MCE_R level. The NEHRP Provisions are based on several previous studies. This paper is oriented toward seismic analysis of ground supported tanks using a vertical response spectrum. While cylindrical tanks have a well-defined and simply determined vertical period, rectangular tanks require the use of peak spectrum response due to the lack of quantified vertical period approximations. A brief discussion of the approach will follow with several examples. Examples will consist of a comparison of vertical response spectrum, ASCE 7-10 code requirements, and reference code requirements (ACI, AWWA and API) for both circular and rectangular ground supported tanks.

Overhead distribution lines supported by utility poles are vulnerable against strong winds. Performance assessment of these systems requires accurate models for various involved components and the system as a whole. Considering that distribution lines are very long and consist of a large number of spans, modeling the entire system is practically not feasible. To address this challenge, this study develops analytical models to capture the boundary effects of adjacent spans on the segment of interest in distribution lines. The proposed model includes equivalent springs and equivalent wind forces to be applied at the boundaries of distribution line segments. The method considers geometric nonlinearities in the response of conductors through an exact solution for their deformed shape under gravity and mean wind speeds. Furthermore, a simplified solution for the deformed shape of conductors is derived and shown to accurately approximate the exact model. These solutions are used to develop a set of stiffness matrix and force vector to simulate the wind response of distribution line segments. Equivalent springs and wind forces representing the boundary effects of neighboring spans are derived considering the variation in the stiffness of the spans and the corresponding wind-induced forces over the length of distribution lines. This approach provides an accurate yet practical method to account for the boundary effects of adjacent spans on the response of utility poles and segments of distribution lines.

The Port of Los Angeles (POLA) recently completed the Berths 144-145 Backland Redevelopment Project. This phase of the first automated container terminal on the west coast of the United States consists of four fully automated stacking blocks and two mini automated stacking blocks. This terminal is one of the first terminals in the world to deploy automated shuttle carriers as horizontal transport in conjunction with automated stacking crane (ASC) blocks. The 33-acre site went fully operational in August 2014. Each 1,100-foot long block has two ASCs, which are mounted on rail and can handle one over-five stack. The ASCs are fully autonomous; they are used to stack containers inside the block and to pick up and deposit containers at both ends of the block. The ASCs require very tight tolerances on their foundation during both construction and operation. Therefore, the crane rail foundation is the most important design element of ASC blocks. The key function of ASC rail foundation is to support the crane loads and maintain the crane tolerances. The ASC foundation in this project consists of rails supported on prestressed concrete ties with ballast. The crane rail foundation design challenges included the variable nature of the subgrade over the length of the ASC block, the influence of adjacent container stacks, liquefaction, seismic loads, crane tolerances, drainage, and conflicts with existing utilities. This paper presents the methodology used to evaluate various crane foundation systems, the design of the rail and ballast-tie foundation system, liquefaction and settlement assessments, and lessons learned from construction challenges.

The in-situ stress field is one of the most important factors affecting the rock stability in an underground powerhouse excavation, and its distribution directly affects the secondary stress distribution caused by excavation. And the regression analysis is widely used to obtain the in-situ stress field and is the basis of rock stability analysis especially for a high geostress region. The underground powerhouse in the Pubugou Hydropower Station is located in a complex geological environment and rockbursts occur frequently during excavation. The in-situ stress and its regression analysis method are applied to analyze rock stability based on the least squares method, FEM and the measured geostress data, and is accomplished in ANSYS in order to acquire the accurate and actual in-situ stress field. Furthermore, basing on the elastic-plastic constitutive model and Drucker-Prager criterion, a 3D finite element numerical model for the powerhouse excavation is established to analyze the stability of the rock mass during the underground excavation. The results show that the tectonic stress is very significant, and the next excavation has little effect on the former excavation in regard to the displacement. In addition, some sporadic tensile, shear and tensile shear failures may occur on the sidewalls of the main powerhouse, at the vault of the main transformer chamber and at the bottom board of the tailrace surge chamber. Medium-level rockburst can also easily occur, particularly at the vaults of the caverns.

Cairo Metro Network is one of the major national projects in Egypt. It aimed at developing underground transportation system to solve the severe traffic problems in Greater Cairo which includes 3 crowded governorates; Cairo, Giza and Qalyubia. The project started in the last decades of the twentieth century where 2 lines were executed. In this century, the project is expanding and more lines are constructed. The tunnel constructed for Cairo Metro Line 3 has a circular cross section that consists of a precast segmental lining thickness of 0.40 m. This paper presents a parametric study on the effects of seismic waves on the tunnel structure through numerous simulations employing the finite-element analysis. Full dynamic analyses were performed employing three different earthquake motions as well as the effect of train-induced dynamic load. Also, the induced tunnel straining actions were studied. The analysis of soil-structure interaction was done using the commercial software PLAXIS. The results proved that the 0.40 m thick circular cross section can safely sustain the expected static, dynamic and seismic stresses.

The accurate estimation of the natural frequency of a turbine-pile-soil system is one of the key design requirements for an offshore wind farm. The natural frequency of the soil-structure interaction system must fall within a narrow window. A FLAC^3D model is used to analyze an offshore wind turbine with a 6.5m diameter pile. Soils were modeled with solid zones using a Mohr-Coulomb model with strain-dependent moduli, the pile with linear elastic liner elements, and upper structure with beam elements. The interface between the pile and soil was also specified. The soil and interface parameters were carefully calibrated with advanced laboratory data including the small strain soil stiffness, and in-situ data from a pile test. Therefore, the numerical model could reproduce the test pile behaviors when subjected to both vertical and lateral static loads. The analysis suggests that both the soil strain-dependent modulus and the lumped rotational masses of the upper structure play significant roles in the turbine natural frequency analysis and should be particularly addressed during the design.

This paper describes field pile tests for offshore wind turbine foundations. Both vertical and horizontal pile load tests were carried out to investigate soil-pile interaction. Finite difference analyses, implementing a Mohr-Coulomb failure criteria with a non-linear elastic stiffness considering strain-compatible effects, were used to perform the back-analysis. The results from numerical modelling are compared with the measured data obtained from optical fiber sensors installed on the internal steel pile surface. It was found that the pile-soil interaction is sensitive to the non-linearity of the soil. The non-linear soil stiffness provides a close match to the pile displacement (and consequently stress-resultants). In addition, the p-y curve method recommended by API was also used for back-analysis. The results from the p-y curve method were found to overestimate the pile displacement and bending moment for large diameter piles in clay.

Electricity generated from wind power continues to grow rapidly as an important part of the energy mix in many regions throughout the world. Advances in technology have led to a rapid increase in wind turbine capacity with the average wind turbine installed in the United States in 2014 being capable of generating about 2 MW of electricity, reflecting an 8-fold increase since 1990. The industry has also seen taller towers being utilized to harness wind resource at higher elevations to take advantage of higher wind speeds and reduced turbulence. Taller towers typically require larger or more robust foundations to support the wind turbine systems and typically translate to higher capital costs for the projects. Balance of Plant (infrastructure and foundation) construction costs make up about 30 percent of capital costs for typical utility scale wind power projects and although there has been a reduction in wind turbine costs over the years, construction costs remain relatively high. Optimized foundation designs contribute to overall reduction in capital costs and would contribute to advancement of renewable energy generation. Geotechnical design is an essential component for the design, planning and construction execution of utility scale wind power developments. Wind turbine foundations have specific design requirements which have to be taken into account to ensure reliable operation of the turbines over a typical design life of 20 to 25 years. It is also important for the geotechnical and structural design aspects to be adequately synchronized in order to develop efficient designs taking into account site specific geotechnical conditions and potential constraints. This paper presents a discussion of important considerations for geotechnical investigations and design for utility scale wind turbine shallow foundations including global stability, bearing capacity, differential settlement, rotational stiffness and cyclic degradation considerations. The paper includes detailed discussion of geotechnical design requirements and design approaches which can be utilized to optimize geotechnical aspects of wind turbine foundations. Merits and limitations of typical approaches such as allowable stress design compared to limit state design for bearing capacity will be discussed.

This paper presents the performance and evaluation of fiber-reinforced asphalt concrete (FRA) in comparison with the rubber modified asphalt (RMA) through laboratory experiments and field observations. Rubber/polymer is believed to enhance the binding properties of the asphalt pavements to increase their engineering characteristics. Some of researchers and highway agencies in the cold regions have considered to add fibers in the currently used RMA to produce fiber-reinforced rubber-modified asphalt concrete (FRMA) to improve its resistance to low temperature cracking and reflective cracking. However, due to the recent cost increase of polymer/rubber material, the possibility of replacing RMA with FRA is being proposed. Thus, it is important to research and investigate the performance between the FRA and RMA. A fiber reinforced asphalt overlay project was constructed on S. Knoles Drive near the Applied Research and Development (ARD) Building at Northern Arizona University. The overlay project (429’Length x 16.75’ Width) was conducted with two types of asphalt mixtures including RMA and FRA to be placed adjacent to each travel lane of the road. Because fiber reinforced asphalt mix has never been used in roadway design and construction in Northern Arizona, it is of interest to understand its resistance to freezing-thawing effect, fatigue cracking, and low temperature cracking. A material testing is undergoing to investigate the performance of FRA pavements in comparison with the currently used RMA pavements so as to provide better understanding of the role played by the fiber in improving the performance of conventional asphalt pavements. Asphalt samples from both asphalt mixtures were collected at the back of a paver from both lances at the time of laydown. These samples were used in the following lab tests: freeze-thaw cycle durability test, and low temperature cracking resistance test using a bending beam rheometer (BBR). The results from the lab tests help generate predictions of low-temperature performance of the two types of asphalt pavement. Field inspections have been scheduled to assess pavement surface conditions. By combing the lab test results with field assessments, the paper provides an analysis to help with decision making in whether it is appropriate to replace currently used RMA pavements with FRA pavements.

An evaluation of the cracking that takes place in asphalt pavements was carried out. Pavement surfaces with low, moderate, high, very high, and critical cracking levels were used in the analysis. The analysis of the intensity of cracking was carried out using the fractal dimension concept, D, from fractal theory. From field and analytical investigations it was determined that: (1) the severity of the cracking in the pavement sections analyzed was reflected in the D values. Low levels of cracking were associated with low levels of D. High levels of cracking were associated with high levels of D. (2) the fractal dimension, D was equal to 1.051 for low level of cracking; 1.1754 for moderate level of cracking; 1.5037 for high level of cracking; 1.7111 for very high level of cracking; and 1.8976 for critical level of cracking (failure). This study also discuss the rehabilitation method of the pavements.

Expansive soil in pavement subgrade experiences volume change due to the seasonal moisture and temperature. For the clear understanding of the subgrade behaviour, it is necessary to study the pavement behaviour in real time which connects the gap between moisture, temperature and suction variation with induced pressure on the pavement and pavement deformation. The current study presents an extensive instrumentation program on a subgrade soil and performance of an asphalt pavement over expansive clay subjected to seasonal variation of moisture temperature and suction. A section over 2- lane State Highway (SH) 342 in Lancaster, Texas, maintained by Texas Department of Transportation (TxDOT) was instrumented with moisture and temperature sensor, water potential probe, pressure sensor and piezometer to monitor the seasonal variation on continuous basis using automated data collection system. In addition, horizontal inclinometer was installed across the pavement and routine topographic survey was conducted to monitor the pavement deformation. Based on the preliminary monitoring results of almost a year, a 5-7% variation of moisture was observed in the subgrade soil whereas; 2 inch of movement was noticed over the pavement. Additionally, a temperature prediction model was developed based on 15 months monitoring data.

Depletion of natural resources and adverse effect of construction waste and reclaimed asphalt pavement materials on environment has ignited the consideration of recycling and reuse of recycled concrete aggregate (RCA) and reclaimed asphalt pavement (RAP) as base material in pavement construction. The composition of recycled base materials vary significantly and mostly depends on the sources. The recycled materials utilized in this study was collected from the Texas Department of Transportation (TxDOT) approved sources. The amount of RAP and RCA varies from 0 to 100% in the combination at 20% interval. The objectives of this study are to determine optimum moisture content and maximum dry density, unconfined compressive strength tests and resilient modulus tests of different combinations of recycled materials at cement content varies from 0 to 6% at 2% interval. The optimum combinations of the different recycled base materials with cement were determined. Layer coefficients for the cement stabilized aggregates were determined to be used in the design of flexible pavements in accordance with the AASHTO design code. The results showed that the recycled base materials i.e., RAP and RCA mixed at optimum combination with 4% and higher cement content can be used as base material in flexible pavement.

Material innovations in composites and ability to predict response of composite structures play an important role in engineering concrete structures resilient to multiple hazards such as dynamic loads. The finite element method is generally used to discretely model fiber reinforcement as beam or truss elements by coupling them with solid concrete elements, and thus assigning the full bond between concrete and fibers. However for modeling fiber reinforced concrete (FRC) structures, this application is hindered by a large number of fibers and associated computational expense. To overcome these limitations, a mesh-free analysis framework is introduced to model interactions between cementitious materials and fibers based on the non-ordinary state-based peridynamics theory. It is demonstrated in two numerical problems subjected to static and dynamic loads that the proposed meshless FRC analysis framework, including a semi-discrete fiber modeling approach, can effectively characterize the pull-out behavior of fibers across cracks without explicitly modeling the fibers and development of local cracks/crack coalescences.

Pavement smoothness is one of the performance measures utilized for pavement maintenance and rehabilitation strategies. The International Roughness Index (IRI), a widely used indicator of pavement smoothness, is required for the Federal Highway Administration’s (FHWA’s) Highway Performance Monitoring System (HPMS). It has also been adapted as a functional performance characteristic in Mechanistic-Empirical Pavement Design Guide (MEPDG), now rebranded as the AASHTOWare Pavement ME Design. The local calibration of IRI prediction model for jointed plain concrete pavements (JPCP) in AASHTOWare Pavement ME Design software requires actual cracking, faulting and spalling measurements, which are not always collected or available with the state highway agencies (SHAs). The primary objective of this study is to examine if the JPCP IRI model can be locally calibrated without doing a local calibration of the primary distress prediction models associated with the IRI model. In this study, the local calibration of IRI model for JPCP pavement systems is performed using two approaches: the coefficients of IRI model are calibrated using (1) locally-calibrated and (2) nationally-calibrated faulting and transverse cracking model predictions. The accuracy of IRI model predictions using both approaches is evaluated and discussed with a focus on achieving reliable smoothness predictions in a cost-effective manner. Comparable accuracy improvement was achieved when Approach 1 was employed in the local calibration of IRI model compared to Approach 2.

Annually millions of tons of reclaimed asphalt pavement (RAP) was generated in the United States of America. The use of RAP and RAP-virgin aggregate mixes in pavement base and sub-base construction are now well acknowledged. Whereas, lack of laboratory and field evaluation is limiting the prospective use of RAP and other recycled material mixes, which may demonstrate more efficiency in terms of cost, depletion of resource, construction waste disposal, and environmental conservation. To illuminate this unfocused sphere, on the basis of laboratory experimental works, this paper describes the strength and stiffness response of different cement treated RAP-recycled crushed concrete aggregate (RCA) Grade 2 base material. Based on the test results of Grade 2, strength and elasticity modulus prediction models for different percentage of RAP were proposed in this study, regardless the amount of cement used. Also, two different design charts for compressive strength and modulus of elasticity were also prepared to facilitate the design of pavement construction in selecting the appropriate aggregate blend and cement content.

Performance-based design considering response to wind demands requires definition of hazard, quantification of the building response, and corresponding acceptance thresholds for various building component actions. Within seismic engineering, two initiatives conducted at about the same time: ATC-33 which led to development of the FEMA 273/274 (1997) rehabilitation guidelines and SEAOC Vision 2000 (1995), made major advances in the definition of the expected seismic performance of buildings designed to conform to the building code by establishing performance matrices covering a spectrum of seismic hazards and associated response for frequent through very rare seismic events. To date, similar evaluations of wind risk and wind response have been discussed in the literature but not concisely established. The purpose of this paper is to present the authors’ viewpoints of the overall performance-based wind design (PBWE) approach, including wind risk, engineering approaches, and appropriate structural response, in order to further inform policy makers, building owners, and the general public regarding building response to common through rare wind events.

This paper describes a method to better understand the risk of life, occupancy and economic losses that could occur during windstorms. Wind performance assessment of a 10-story steel-frame office building was accomplished by determining the building response for increasing levels of wind intensity using modified wind history records from wind tunnel testing. The sensitivity of key building components—both structural components and non-structural components—to wind-induced motion was determined by adapting tools and procedures originally developed for a seismic performance assessment. The results indicated that the building was habitable during service-level windstorms, and that damage to cladding, and a need for the repair of structural components, was expected during strength-level and near-collapse level windstorms.

The current prescriptive design philosophy that relies simply on meeting requirements stipulated in standards is shifting towards a performance-based design (PBD) approach for achieving designs that rationally meet society’s need for a truly safe built environment. Extensive research has facilitated the successful adoption of PBD in earthquake engineering, but the same cannot be said for wind engineering. Therefore, the need exists to initiate a similar effort by defining a framework that fully embraces the concepts of PBD during the design of building systems to resist severe wind events. This paper illustrates the development of such a PBD framework. In particular, a method is proposed specifically for multi-story wind excited buildings in order to mitigate structural and non-structural damage and loss. In particular, the post-yield behavior of the structural system is modeled using the theory of dynamic shakedown, therefore providing a full portrait of the post-yield behavior without the need for computationally expensive non-linear finite element models. A case study is presented illustrating the practicality of the proposed PBD framework.

Performance-based engineering (PBE) is a methodology that requires specification on a range of performances or target reliabilities for structures of different importance. Information on these ‘performance levels’ require a probabilistic assessment of the potential factors that may influence a design, including information on the hazard, load, resistance, loss estimates, expert opinion and public perception. This paper describes one such probabilistic assessment in the development of empirically-based fragility functions for tornadoes using damage assessment data and a tornado wind field model for the 22 May 2011 Joplin, MO tornado. The damage assessment data was collected during field surveys of more than 1,240 structures in the aftermath of the tornado, using provisions of the Enhanced Fujita (EF) Scale to assess the damage. The wind field model was developed from the tree-fall patterns noted in the damage path of the tornado. Fragility functions were developed for the degrees of damage (DOD) associated with one- and two-family residences in the EF Scale. The empirically-derived fragility functions were progressive in nature, with median wind speeds varying from 33.6 m/s for initiation of visible damage to 85.2 m/s for complete destruction. These functions were compared to existing fragility functions for straightline winds to evaluate potential differences in failure mechanisms for structures exposed to tornadoes. Wind speeds associated with the median failure probability were used to estimate load factors, defined as the square of the ratio of the straightline wind speed to the tornado wind speed. Structures tended to fail at lower wind speeds in tornadoes than in straightline winds, with load factors between 1.32 and 1.51. A fragility assessment in the context of PBE naturally requires attribution and quantification of all uncertainties. Uncertainties in the fragility functions were estimated in this study through cross-validation methods. Preliminary results show variance in fragility parameters is higher for higher damage states but all damage states have uncertainty less than 10%.

This paper discusses subdrain outlet condition and performance in Iowa roadways. A forensic test plan was developed and executed during wet summer conditions covering over 230 and 120 drain outlet locations of the newly constructed jointed plain concrete pavement (JPCP) and the hot mix asphalt (HMA) over JPCP sites, respectively. The tufa formation (i.e., calcium carbonate deposits) is the primary cause of drainage outlet blockage in newly constructed JPCP sites using recycled portland cement concrete (RPCC) as a subbase material. Lesser tufa formation from the use of RPCC base in JPCP was observed with the: (a) use of plastic outlet pipe without the gate screen type rodent guard, (b) use of blended RPCC and virgin aggregate materials. The observations of moisture-related surface distresses nearby blocked drainage outlet locations in HMA over JPCP indicates that compromised drainage outlet performance could accelerate the development of moisture-related distresses in HMA over JPCP.

While asphalt-concrete layer properties are more sensitive towards temperature variations, the subgrade stiffness have proven to be quite sensitive to moisture content fluctuations. When embankments are needed during the pavement construction, the soil must be compacted at a particular moisture-density condition to reach homogeneous properties. Due to construction variability, the as-compacted conditions might vary from the required specifications. This is of particular interest when dealing with compacted fine grained subgrade materials due to the influence of soil permeability in the seasonal moisture content fluctuation. The main objective of this study is the evaluation of the structural capacity and pavement performance due to the variability associated with the as-compacted moisture and density conditions, for different climatic regions. Three types of materials ranging from silt to clay were used in the analysis. Weather information from three locations was collected to represent different climate regimes. The pavement performance was analyzed using the Mechanistic-Empirical Pavement Design Guide (MEPDG) procedure by using the response of the pavement to three major distresses: fatigue cracking, rutting and thermal cracking. Two different levels of input accuracy were compared: Level 2, which uses simple index material and compaction properties and Level 3, which uses just the simple index material properties to estimate the resilient modulus. Results indicated that the soil compacted to optimum moisture content predicted less amount of distress when compared to the wet or dry optimum conditions for the low plasticity soils; whereas the predicted distresses increase with the increase in the as-compacted moisture content for the high plasticity soils. When compared with ratio of optimum condition, IRI had a maximum increase of 5% in Chicago and Atlanta region exhibited a fatigue cracking increase of 40% while Phoenix area showed a lot of rutting increase of 30%. The difference in the distress results obtained for Level 2 and Level 3 analyses were not significant for the soil compacted at optimum condition, but the dry and wet of optimum conditions resulted in significant larger differences that depended on the location or climate where the pavement is constructed.

Modern seismic protection technologies in the forms of isolation bearings and fluid dampers can be used to improve the seismic responses of highway bridges. This paper aims to use the performance-based evaluation approach to investigate the seismic performances of a newly constructed highway over-crossing in California that is equipped with isolation bearings and fluid dampers. A simplified 2D bridge model representing the transverse response of the bridge is adopted that take into account of nonlinear behavior in bridge, isolation devices and fluid dampers as well as soil-structure interaction effects. Fragility curves are derived by PSDA for pier columns and base isolators first then combined into a composite system curve based on the repair cost ratio of these two components for each damage state. The efficiency of using isolation bearings and fluid dampers is investigated by comparing system fragility curves of three different cases, i.e., the as-built bridge, the isolated bridge, and the bridge installed with both base isolators and fluid dampers. Furthermore, utilizing a multi-objective genetic algorithm, the optimum combination of mechanical parameters of isolation bearings and fluid dampers are identified. The study shows that the optimum design of isolation bearings and fluid dampers are able to reduce the bearing deformation and deck acceleration simultaneously and minimize the overall damaging potential of the bridge.

Northern Haiti is vulnerable to damage from potential earthquakes that can result in catastrophes nearing or exceeding the 2010 event. The Septentrional-Oriente Fault Zone passing close to the major cities including Cap Haitien, Ft. Liberte, and Port de Paix, was a significant contributor to historical seismicity within the region, including the 1842 M8.1 Cap Haitien Earthquake that led to approximately 5,000 deaths. Given the history of this fault and its tectonic setting, there is significant potential for future strong ground motion and widespread death and destruction. To address the seismic vulnerability of Northern Haiti, a comprehensive risk assessment of the building population was conducted. The key components of the program included: a) performing geotechnical investigation to develop microzonation maps for the major cities; b) performing surveys of areas to collect exposure data for the sites; c) extrapolation of collected data to cover the entire effected areas; and d) performing probabilistic risk analysis to estimate fatalities, financial cost, and the number of required temporary housing for the area. The results of the study can then be used by the government and international agencies to allocate resources to focus and maximize the outcome of earthquake risk mitigation program.

This paper focuses on seismic fragility analysis of a semi-actively controlled high-rise building with magnetorheological (MR) dampers. Many control devices and methodologies to reduce seismic damage of the building structures have been developed. However, little research has been carried out to evaluate seismic fragility of controlled buildings with a broad range of seismic hazard levels. In this study, a 9-story steel moment-resisting framed (MRF) building is selected as a case study structure, and an advanced decentralized output feedback polynomial control (DOFPC) algorithm is applied. Seismic fragility relationships are investigated using a system reliability approach and are compared those results based on 41 earthquake ground motions with two different hazard levels. The preliminary results of fragility estimate based on the system reliability approach show that the differences on seismic performance for multiple performance-based control designs against 41 earthquake motions match well with the initial objectives of performance-based design.

Maintenance, rehabilitation and replacement of existing bridges by using cost effective management are increasingly important topics in efforts to deal with aging and deteriorating infrastructure. Recently, engineers have shifted the emphasis from design and construction of new bridges to maintenance and rehabilitation of existing bridges. This paper uses the structural reliability method with a predefined performance function to assess the component performance of the main load carrying members of an inner span in a multi-span bridge. The performance of the components is a function of various random variables with certain probabilistic distributions. The analysis is extended using the same performance function to evaluate the reliability of the bay as subsystem and bridge as a system. System reliability in this case is defined as the probability that a system (bridge) performs its intended function under operating conditions for a specified period of time using second order reliability method (SORM) and Monte Carlo simulations. In addition, deterioration in the main carrying elements (components) due to environmental impacts is introduced and the sensitivity parameters for certain random variables are re-evaluated to determine the inspection and maintenance period of the bridge. The deterioration is imposed as a percentage reduction in certain random variables. The paper involves use of multi reliability analysis at component, sub-system and system levels. Results show that probability of failure (P_f) increases with decrease in distance of the bridge from source of deterioration. Reliability index (β) decreased with increase in the age of the bridge because of corrosion of reinforcing steel. Results also show that the rate of probability of failure for bridges exposed to deteriorating effects increased dramatically after 45-50 years.

This paper proposes a set of probabilistic demand models of bridge components using the Bayesian parameter estimation method. To develop probabilistic demand models of individual bridge components, the material, structural, and geometric properties used in the bridge models serve as independent variables and the response data of engineering demand parameters for individual components monitored from the analyses serve as dependent response variables. To illustrate the proposed methodology, a typical reinforced two span, three frame curved concrete box-girder bridge in California is selected as a case study. Probabilistic numerical bridge models are developed, and then nonlinear time history analyses are performed using a set of ground motions representative of the seismic hazard. The significant input parameters are identified through a stepwise removal process in the Bayesian approach. The demand models generated in the Bayesian approach provides a more reliable estimation of the seismic demand compared to the traditional approach in which the ground motion intensity measure is the only input parameter.

This paper presents a procedure for inverse analysis of braced excavations based on the extended Kalman Filter formulation. Prior estimation of soil parameters for analysis and design of braced excavation is first made using limited laboratory data obtained from site investigation. Then during the staged excavation, an extended Kalman Filter formulation is used to update the estimated soil parameters based on monitoring data of the maximum ground settlement and wall deflection. The updated soil parameters are then used to refine the predictions of the soil-wall-support system responses in the subsequent stages of excavation, as well as to evaluate the damage potential of adjacent buildings at the final stage of excavation. A case study is utilized to demonstrate the effectiveness of the developed procedure for improving the predictions of the excavation-induced wall and ground responses. Furthermore, a more rational assessment of the damage potential of the adjacent buildings is yielded through this updating procedure. The proposed procedure is demonstrated to be an effective tool for improving the predictions of the ground responses and building damage potential in a staged excavation.

Beneficial use and recycling of industrial byproducts promotes sustainability in roadway construction. An estimated 15 million tons of waste sands are produced from foundry operations (e.g., casting) in the US annually, out of which less than 28% is recycled and the remainder is landfilled. High-volume structural fill applications such as highway embankments can possibly use the majority of the foundry sands. One of the primary impediments to beneficial reuse of foundry sand in large volumes, however, is uncertainty with respect to its material and engineering properties, including compressibility and volume change. Foundry sand with bentonite binder may exhibit excessive permanent deformations under long-term loading. Compressibility of foundry sands from five different sources in Wisconsin were evaluated in a systematic suite of one-dimensional (1D) and three-dimensional (3D) compression tests. Compacted foundry sands are more compressible than compacted natural sands. Compressibility of foundry sand increases with bentonite fraction and the rate of secondary compression ratio increases with time. Compressibility parameters for foundry were quantified based on bentonite content. Recommended parameters can be used in numerical analyses to estimate creep deformations of embankments constructed with foundry sands at different stress levels, bentonite content, and time since construction.

In the United States, nearly 300 million tires were discarded in 2003. Since rubber tires are not biodegradable and occupy a large portion of available landfill space, 35 states have banned whole tires from landfills, while 11 states have banned all tires from their landfills. As a result, many tires are improperly discarded posing several health and environmental concerns. Crumb rubber has been used in a variety of applications in geotechnical engineering including in highway pavements and backfills of retaining walls. In each of these applications, the rubber tire was used as an individual material, but the use of crumb rubber to modify soil may provide additional benefits. In this study, MH and CH types of soils were modified using different sizes and quantities of crumb rubber and used to evaluate the improvement in geotechnical properties. A Harvard miniature compaction apparatus was used to determine the maximum dry density and optimum moisture content for each sample that was, then, tested in an unconfined compression device to measure the undrained shear strength. Direct shear tests were also conducted on the soils modified with crumb rubber. Moreover, permeability and consolidation characteristics of the clay-tire mixtures were also evaluated for all mixtures. The results showed that for MH soils, the maximum dry density increased as the percentage of crumb rubber in the soil increased, while increasing the size of the crumb rubber increased the maximum dry density; no significant variation in the optimum moisture content was found with the addition of crumb rubber in the MH soil. In the CH soil, as the size of the crumb rubber increased, the maximum dry density of the modified soil increased with the highest maximum dry density when 2%-4% crumb rubber added. The optimum moisture content was found to increase as the size of the crumb rubber increased with the lowest optimum moisture content at 2% crumb rubber content. The highest strength was observed at 2-4% rubber in MH soils and at 4% rubber in CH soils. In general, the increase in strength was found to be larger when a larger size of the crumb rubber was used to modify the soil. Similar effect was observed in the coefficient of consolidation and permeability values. From this study, it is concluded that crumb rubber can be effectively used to improve the compaction and strength characteristics of weak soils.

The ring shaped–steel plate shear wall (RS-SPSW) system is a new structural system that improves upon conventional SPSWs by mitigating buckling of the web plate. The RS-SPSW is characterized by cutting a pattern of rings connected by diagonal links into a solid web plate. The RS-SPSW mitigates the challenges of conventional SPSWs by eliminating undesirable buckling limit states through an innovative yielding mechanism. The elimination of buckling results in stable hysteretic behavior with high levels of energy dissipation and large amounts of system ductility. Previous computational and small-scale experimental studies have been conducted to validate the RS-SPSW concept. Currently, large-scale, 10 feet by 8.5 feet specimens are being tested to further validate the RS-SPSW system. The results from two of the four RS-SPSW specimens are presented. This paper discusses the observed cyclic response, energy dissipation, and deformation capacity of the RS-SPSW experiments.

Recycled asphalt pavement (RAP) can be beneficially reused as fill material in highway embankments or backfill behind retaining structures. In this study, deviator creep response of RAP compacted at different temperatures was investigated through a series of triaxial compression tests conducted at sustained deviatoric stresses. Test results showed that the compacted RAP represent classic creep response similar to soils. Creep rupture was observed at deviator stresses higher than 70% of the compressive strength. Compaction and compression at elevated temperatures increased the shear strength and reduced the creep strain of the RAP specimens. To minimize creep strain and potential for creep rupture, construction of structural fills containing RAP is recommended during warm months of the year.

Concern and interest about the environment and ecologic systems have promoted the usage of earth as a construction material. Technology advancement has resulted in the evolution of old adobe and cob into compressed stabilized earth blocks (CSEBs). Compressed stabilized earth blocks are prepared by compressing the soil-stabilizer mixture at a particular stress. In order to accomplish the required strength, cement has been used in a regular basis as stabilizing agent, at proportions that are still harmful to the environment. CSEB blocks have various advantages related to cost reduction, energy efficiency and environmental friendly and therefore, it is of interest to find means to reduce the amount of cement used in their construction without affecting its dry strength and durability. In this study, natural fibers were used along with lower proportions of cement than those commonly used in practice and varying fine content in the soil to assess its effect on the dry strength and durability of the blocks. Blocks were compacted with 10MPa stress and prepared by using 7%, 5% and 3% cement along with varying fiber content ranging from 0.25% to 2%. The effect of fine content, cement and fibers on strength and durability of the natural fiber-reinforced blocks was studied. Sand/clay fractions of a native soil from the Phoenix area were used to fabricate the blocks. Preliminary results indicate that the compressive strength reaches a maximum value for blocks with 30% fine content; blocks with 5% cement withstand the durability test; an increase in fiber content decreases the strength of the material; and finally, the soil-cement loss was minimal for blocks with 50% fine content.

The Massachusetts Bay Transportation Authority (MBTA) is addressing accessibility throughout their facilities. Improvements at the Commuter Rail Station in Salem, Massachusetts include a five-level parking garage, a pedestrian bridge, two accessible elevators, and a full-length accessible high-level platform, as well as a passenger drop-off/pick-up area, secure bicycle parking, and improved traffic flow patterns for buses and taxis. The project site is bound by North River to the north, and is retained by a 12 feet high seawall along the river. Subsurface conditions generally consist of fill overlying loose, potentially liquefiable saturated sands, overlying very soft to soft marine clay deposits extending to till and rock at about 60 to 80 feet depth. The site was classified as a seismic Site Class F, which called for a site-specific site response analysis and structurally robust parking garage building. Deep foundations in the form of drilled shafts bearing on rock were recommended for structural support of the garage. Through cooperation of the structural and geotechnical teams and evaluations of many options, ground improvement in the form of vibratory stone columns (VSCs) was recommended to address the liquefaction and lateral spreading potential, and improve the seismic site classification to Site Class E. The project team evaluated value-engineering options. The final design consisted of the installation of controlled modulus columns (CMCs) below the garage and bridge footings, and VSCs below the parking garage and platform. The project involved developing detailed specifications for ground improvement and a verification program to assess the effectiveness of the VSCs. The unique site conditions required additional coordination between the geotechnical and structural design teams, as well as the construction team during the design phase of the project. The collaboration between the teams was integral in allowing the project to move forward, ultimately saving the client millions in construction costs.

The effect of shaking history on cone penetration resistance, cyclic resistance ratio, and their correlation to each other for saturated sand is examined using centrifuge model tests. Prior laboratory and centrifuge modeling studies have shown strain history can have a strong effect on the cyclic strength of sand, but data describing how these effects track with cone penetration resistance are lacking. The effects of shaking history on cone penetration resistance and cyclic strength are investigated using centrifuge models of saturated Ottawa sand on a 1-m radius centrifuge with a 6-mm diameter cone penetrometer. The centrifuge models are subjected to a series of shaking events at progressively increasing amplitudes until liquefaction is triggered. This motion is repeated until the sand no longer liquefies. Cone penetration tests are performed before any shaking, after liquefaction is triggered, and after liquefaction no longer occurs. Inverse analyses of accelerometer array data are used to compute profiles of dynamic shear stresses and strains. The results are used to examine the effects of prior strain history on cone penetration resistance, cyclic resistance ratio, and their correlation to each other. The centrifuge test results are also compared with a case history-based liquefaction triggering correlation.

Seismic liquefaction assessments continue to evolve as the industry continues to refine and improve current analytical methods resulting from additional liquefaction case history data being acquired. However, one area that is still somewhat in its infancy is the effect aging has on the cyclic strength of soils. Several recent studies have been carried out and reported in the literature that conclude aging is a phenomenon that is real. If that is the case, then aging needs to be incorporated into our current liquefaction analysis procedures to avoid the unnecessary high cost of remediation and/or wholesale cancelation of projects. However, questions still arise regarding the details of how aging is specifically incorporated in the liquefaction susceptibility analysis.

Analyses of liquefaction-induced lateral spreading during earthquakes often contain simplifying assumptions about the stratigraphy of a site (i.e., selecting representative cross sections and properties), which can be a major source of uncertainty in the estimated deformations. This paper examines the potential for liquefaction-induced lateral spreading in a deposit of interbedded sand and clay using nonlinear deformation analyses. The soil is modeled as a binary mix with varying percentages of potentially liquefiable sand and non-liquefiable clay. The location of each soil type is represented through different realizations of interbedded stratigraphy generated using a probabilistic geologic model and a correlation structure consistent with natural fluvial deposition. The procedures used to generate these realizations and perform the dynamic numerical simulations are described. Different distributions of sand and clay are examined to determine how the percentage of liquefiable material influences the magnitude of surface deformations. The undrained strength of the clay is varied to further explore how this affects the relationship between deformation and sand percentage.

For the safe design of civil engineering structures such as earth dams which are located near strike slip fault segments, geotechnical engineers need a reliable method to estimate the vertical ground deformations that fault movement will induce at the site of the proposed earth structures. In this study, the vertical ground deformations induced by the movement of a strike-slip fault segment are calculated using the linear elastic fracture mechanics theory. The ground deformations estimated using this theory and the deformations experienced by the ground surrounding a strike-slip fault segment located in China compared well.

Observations will be provided of a number of sites where existing buildings are located over fault traces that have or could rupture during an earthquake. Case histories will be provided where either new structures were designed to accommodate fault movements or foundations of existing structures were modified to improve performance during such events. Several situations will be discussed where foundation improvements of an existing building may be possible from a technical sense, but may be precluded by existing codes (such as California’s Alquist-Priolo Act) and whether modifications should be made to these codes to permit mitigation measures for the building owners to improve the performance of their buildings.

The Anchorage Landslide following the 1964 Alaska Earthquake, damage to the Moss Landing Marine Laboratory after the 1989 Loma Prieta Earthquake, and severely distressed buildings founded on clays following the 1985 Mexico Earthquake have emphasized the current deficiencies in our understanding of the cyclic and post-cyclic behavior of clays. Although researchers have begun evaluating the behavior of clays during and following cyclic loading, information presented in the literature is inconsistent. This study systematically evaluates the effect of plasticity characteristics and mineralogical composition on the cyclic behavior and the post-cyclic shear strengths of normally consolidated clays. Eighteen samples were prepared in the laboratory by mixing kaolinite with quartz (KQ) or montmorillonite with quartz (MQ) and tested in a cyclic simple shear device under a sinusoidal loading at a frequency of 0.5 Hz. The samples were then sheared monotonically to determine the post-cyclic shear strength. In addition, cyclic simple shear testing was conducted at a consulting firm for 12 natural samples. Using the test results, cyclic strength curves were developed to represent seismic performance levels of immediate occupancy (2.5% double amplitude, DA, shear strains), life safety (5%) and collapse prevention (10%). The cyclic strength curves showed that in KQ mixtures, a smaller number of additional cycles of loading were required to cause 10% DA strains after the sample had experienced 2.5% DA strain in comparison to MQ mixtures. The cyclic resistance was found to increase as plasticity index (PI) increases. The cyclic strength curves were also observed to become increasingly linear as PI increases in KQ mixtures, but the opposite trend was observed in MQ mixtures. The lower bound post-cyclic strength was found to be 45% to 100% of the static shear strength. Moreover, the post-cyclic shear strengths were significantly higher than the strength recommended by the current guidelines. Based on the results, current guidelines for seismic evaluation of clays may need to be re-visited to ensure both safe and economic design of infrastructure.

Undrained shear strengths are imperative in evaluating the stability of embankments founded on normally and overconsolidated clays. Variation of undrained shear strength of clays with over-consolidation ratio (OCR) has been studied to some extent. However, the effect of activity and mineralogy on OCR based undrained shear strength variation has not been studied in detail. In this study, three mixtures of kaolinite with quartz were consolidated at the OCR of 1, 2, 4, 8, 16, and 32 using an oedometer. The samples were, then, tested in a static NGI-type static simple shear device confined by a rubber membrane and a stack of Teflon coated rings. The study result showed that the undrained strength ratio increased by an increase in OCR. The increase in strength with OCR yielded a unique relationship for soil having kaolinite as clay mineral. The SANSHEP model was utilized to estimate the undrained shear strength of tested clays at different OCRs for varying activity values.

Landslides and slope failures cause an annual loss of billions of dollars of properties and death of thousands of people. In the past few years, the loss due to landslides mainly after pre and post-earthquake rainfall events increased significantly. In this study, a systematic analysis was performed on the effect of rainfall after the slope is shaken by different scales of cyclic motions and vice versa. Soil samples collected from a landslide site at a compacted fill location in Southern California and were compacted separately at different void ratios and angles of inclinations. The slopes were instrumented with numerous accelerometers, tensiometers, and inclinometers. The slopes were first subjected to cyclic motions at different magnitudes and frequencies and post-shaking spatial deformations were measured. Then the slopes were subjected to different magnitudes of rainfalls until they got saturated and pore spatial distribution of wetting front, pore pressure, and deformation were measured with time. Likewise, the slopes were first subjected to rainfall and same cyclic motions were applied after the rainfall event. Deformation, pore pressure, and movement of wetting fronts were measured to compare the effects of each triggering factors on slope stability. The result shows that both pre and post earthquake rainfall effect dramatically increase slope deformation and reduce the factor of safety of the slopes.

The March 22, 2014 Oso Landslide in Washington was the most deadly landslide on record in the United States. Forty three people were fatally injured in a matter of seconds. The slide devastation covered more than 200 acres. The distance from the top of the head scarp to the furthest limits of the landslide impact was over 6,000 ft. The elevation difference was about 600 ft. More than 20 homes were destroyed in a matter of seconds. Before and after images taken by the author will be used to show how he thinks this slide occurred and why the destruction was so severe. In 2002 the author first photographed and examined the site. Since then, the author has made more than 60 flights over the site at various times and taken more than 1,000 images over the 12 year period. The slide area has been periodically moving for more than 100 years and has been examined by others prior to the author’s involvement in 2002. The most recent previous slide at this site occurred on January 25, 2006. It was different from many of the previous slides, and possibly larger than any those that have occurred at the site in the last 80 years. Images taken before and after the 2006 landslide demonstrate the differences in the mechanisms of the 2014 slide and all documented previous slides. The photographs give strong clues about why the 2014 slide was so destructive. Others studying the landslide have unofficially implied it was a deep seated landslide and then later a debris avalanche flow. The author is convinced it was neither. The author will use his pictures and long term observations to show what he believes happened at Oso.

There are a large number of constitutive models developed to simulate the behaviour of embankment dams subjected to static and dynamic loading. However, it is difficult to evaluate the performance of such models without well recorded data from case histories. The strong ground motion of Wenchuan earthquake which hit Zipingpu Dam in China in 2008 has provided an excellent benchmark to study the behaviour of large modern rockfill dams subjected to seismic loading. The performance of the dam during construction and prior and after the earthquake loading has been recorded with good accuracy and provides a reliable database to examine the reliability of available constitutive models. In this paper, an advanced bounding surface plasticity model has been used in a series of numerical analyses to study the static and dynamic behaviour of Zipingpu Dam. The model can take in to account particle breakage that may occur in monotonic and cyclic loading of rockfill materials. The material parameters required for the model are calibrated based on the results of monotonic and cyclic triaxial tests on the rockfill material. The results of the numerical simulation are compared with the displacements measured during impoundment and after the earthquake.

Stage construction is an essential method for the building of tall embankments on soft foundation soils. During stage construction, soft foundation soils consolidate and undergo an increase in effective stress, a reduction in void ratio, and an increase in shear strength. However, the combination of soft foundation soil and tall embankments is prone to large settlement deformations and potential failure due to the contribution of lateral movements to vertical settlements. This study documents numerical parametric studies to evaluate failure mechanisms of the mechanically stabilized earth walls founded on soft soils. The number of analyzed parameters was reduced by conducting a dimensional analysis. Analyzed parameters include boundary conditions, soil properties (i.e., backfill friction angle, Young’s modulus, undrained shear strength, Poisson’s ratio) and embankment geometry (i.e., wall height and reinforcement length). Results indicate that decrease in backfill friction angle, increase in embankment height, decrease in undrained shear strength lead, of course, to a decrease in factor of safety, however changes in Young’s modulus and Poisson’s ratio do not contribute to the factor of safety but directly affect the settlements. These results show the limitation of considering allowable stress design and serviceability in the interpretation of large and complex foundation structures.

The main goal of this paper is to make physical vulnerability curves for various of building structures in Korea to enable a quantitative assessment of debris flow risks. The physical characteristics of debris flows were analyzed based on 8 debris flow disasters. A total of 19 buildings that were damaged during these events were investigated in detail to determine the characteristics and patterns of the damage. The physical vulnerability was obtained from the relationship between the degree of building damage and the intensity of the debris flows. The intensity of the debris flow such as flow depth, velocity, and impact pressure was analyzed by empirical method and numerical method. Three different vulnerability curves were obtained as functions of the debris flow depth, the flow velocity and the impact pressure. The impact pressure of debris flows corresponding to slight damage to RC buildings could result in complete destruction of non-RC buildings. The physical vulnerability curves described here have potential applications in quantitative assessment of the structural resistance of buildings to debris flow events.

It is anticipated that the future climate in Korea will cause increased vulnerability towards rapid mass movement events. As the criteria for assessing mass movement vulnerability to climate change in Seoul, the sensitivity and exposure indices were employed. To access the landslide sensitivity index, a landslide susceptibility model which has been developed by using maximum entropy model (MaxEnt) under different future rainfall projection. The projected rainfall climatic scenario was adopted from concentration pathways (RCP) scenarios 4.5 and 8.5 and to compare results. The area identified as high susceptible was considered for the runout propagation. For this purpose modified multi-directional algorithm was used. The buildings were quantified as exposure in runout hazards in different climatic scenario.

A heavy rainfall occurred in October 2013 in a volcanic island of Izu Oshima. Induced by a typhoon, this rainfall produced more than 800 mm of precipitation in one night and a huge slope failure occurred in a slope that had been stable for many centuries. The debris flow claimed 39 lives in mid night. This tragedy was investigated and the present paper addresses some of the lessons. The volcanic slope consists of layers of different materials and their behavior is complicated. Of particular interest is the piping holes that suggest significant destabilization of the slope due to extra pore water pressure from the underground hydrological environment. By considering this effect by simple analyses, the roles played by lava layer was understood. After the disaster there remains many ridges whose stability in future was of public concern. The present study interpreted the collected bore hole data to suggest that those ridges are relatively stable because of the underground lava topography. Finally, ideas for future early warning and evacuation were discussed.

Seattle was one of the first cities to use performance-based seismic design (PBSD), with designs beginning in the late 1990s. This paper presents the history and practice of the geotechnical engineer’s role in PBSD of high-rise buildings in Seattle. The standard of practice for seismic design continues to evolve, with changes to codes and increased understanding of seismic hazard and geologic conditions. The Seattle Basin and its effects are unique to the region and, if neglected, can result in an unconservative design. The northern splay of the Seattle Fault is located just south of Downtown Seattle and the Cascadia Subduction Zone is nearby to the west. This paper describes how these conditions have been accounted for in seismic hazard analysis and ground motion selection and scaling for PBSD of high-rise buildings.

This paper presents a novel coupled model of discrete element method (DEM) and finite difference method (FDM) to investigate the load-deformation of stone columns reinforced soft clay. In the proposed model, the soft clay domain was modelled by the continuum method using FLAC and stone column was modelled by the discrete element method using PFC2D. Algorithms and mathematical framework to assist coupling between the two domains were introduced, in which the DEM transfers forces and moment to the FDM and then the FDM provides an update of displacements to the DEM. The predicted load-deformation responses obtained from the coupling model reasonably agreed well with data measured experimentally, indicating that the proposed coupling discrete-continuum model could capture the deformation behavior of stone column stabilized soft clay. Evolutions of contact force distributions developed in stone column at varying levels of settlement were presented. Shear stress-strain contours induced in the surrounding soft soils were also investigated.

A response of the actual end bearing heat exchanger pile to combined mechanical and thermal loads is predicted by computational modeling. The pile is surrounded by a layered soil profile consisting of four different clay layers while the pile tip is slightly embedded into the bedrock. Most of the material properties relevant for the computational model were obtained based on laboratory tests that were carried out during the site investigation. Furthermore, the influence of mechanical, thermal and hydraulic properties of soil layers on the pile response are investigated by considering four additional homogeneous soil profiles, each one of them being a single soil from the actual layered soil profile underlain by the bedrock. It is found that the response of the pile in soils A1 and A2 on one hand, and the response of the pile in soils B and C on the other hand provide two extremes that bound the response of the pile embedded into the actual layered soil profile. The latter very well with the experimentally observed response, except perhaps for the very shallow depths.

Strong ground motions from the Mw 6.6 2007 Niigata-ken Chuetsu-oki earthquake were recorded by a free-field downhole array installed near the Service Hall of the Kashiwazaki-Kariwa nuclear power plant site. At the vertical array, a reconnaissance team observed ground settlements of up to 25 cm, which was later corroborated from a 2009 site investigation. Field tests suggested relative densities of approximately 30-40% in the upper sand layer which overlaid clayey bedrock. Samples from the site investigation were used to develop a material specific volumetric strain material model for the corresponding relative density. Using results from ground response analyses and the volumetric strain material model, ground settlements of approximately 13 cm due to horizontal shaking only were estimated. The estimated settlement increases to 19 to 20 cm when vertical ground motions are also considered. This range of settlement from seismic compression is in close agreement with the observed settlement near the site.

Construction over soft clay sites has remained a major challenge all over the world as there are numerous problems associated with such sites such as low foundation support, huge settlement and large deformations during a seismic event. One alternate to construct civil engineering structures on the foundations having weak clays is modifying soils with soil-cement mixtures. The proportion of cement and curing time plays important role in the geotechnical properties of modified soils. The present study investigates the static and dynamic behavior of cement modified clay. Granular Kaolin clay which is commercially available as Hydrite Flat DS with PI=17 was mixed with cement at cement proportions ranging from 2 to 10%. Compacted soil-cement samples were prepared at a water content equal to the corresponding optimum moisture contents of the soil-cement mixtures. These samples were wrapped with plastic sheet and stored in an air tight container for 7 and 14 days. Various laboratory tests such as unconfined compression tests, direct simple shear tests, and cyclic simple shear tests were conducted on the soil-cement mix samples cured for 7 and 14 days. The study results were helpful in determining the unconfined compression strengths, modulus of elasticity, drained and undrained shear strength parameters, pore pressure behavior, stress paths and stress-strain behavior of the cement modified clay under static and cyclic loading conditions.

As part of the 1.4 billion U.S. dollars Design-Build Interstate Highway 35 East (IH-35E) project running through Dallas and Denton Counties in Texas, over 120 mechanically stabilized earth (MSE) retaining walls and 16 bridge widening are planned along the 30-mile alignment. This paper describes the methodology implemented to obtain site specific correlations of shear strength parameters (effective cohesion and friction angle) in residual clays derived from the Eagle Ford shale, Woodbine sandstone formations, and alluvial soils from 3 valleys for the analysis of the MSE retaining walls. These correlations are derived from borings drilled along the project alignment and consist of field measured descriptions, SPT and Texas cone penetrometer blowcounts, and laboratory index property tests. Historically, the soils derived from Eagle Ford shale are known to be problematic resulting in stability issues especially when modified from their in-situ conditions. These soils are overconsolidated, in the laboratory we quantified the overconsolidation ratio (OCR) between 2 and 6. To characterize these soils, 13 consolidated-undrained (CUIC) triaxial tests at peak principal stress ratio (39 data points) and 13 stress-history controlled direct simple shear tests on reconstituted samples (39 data points) were completed to assess OCR against effective cohesion and friction angle. Twelve 1-D consolidation tests were performed to evaluate stress history in the laboratory and estimate preconsolidation pressure and OCR range. The results were analyzed along with a database containing 17 laboratory CUIC triaxial tests (51 data points) from previous projects within the area. A correlation matrix with five Mohr-Coulomb drained effective strength envelopes at peak principal strength ratio and soil OCR has been proposed for the lean (CL), fat (CH) and sandy lean (SC) clays within these formations.

The effect of prior strain history on cyclic strength and cone penetration test (CPT) tip resistance of non-plastic silica silt is evaluated. A series of undrained cyclic direct simple shear (DSS) tests on slurry deposited specimens are performed to characterize cyclic strength. Cyclic strengths are evaluated for maximum shear strains of 1% and 3% in 15 cycles. Drained CPT tip resistances are estimated from simulated cavity expansion limit pressures. Cylindrical cavity expansion simulations are performed in the finite difference program FLAC using a modified version of the MIT-S1 elasto-plastic constitutive model. The evolution of cyclic strength and simulated CPT tip resistance during a series of cyclic loading and reconsolidation stages is presented. The developed relationships between cyclic strength and CPT tip resistance are shown to track the curvature of corresponding semi-empirical q_c1Ncs-CRR triggering curves. Dependence of the presented relationships on failure criterion (maximum shear strain) is shown to be qualitatively consistent with the literature.

This work aims to be an initial investigation to the use of geophysical and limited geotechnical data to obtain soil and stratigraphy characterization. This approach is essential for developing countries where geotechnical data is typically scarce and expensive. This type of consolidation was used on a study area in Lebanon that consists of a failed slope. A consolidation of data from surface wave measurements, electrical resistivity, and in-situ data was carried out where each gave a part of the description of the site. The surface wave measurements revealed that the seismic bedrock depth was not reached in the range of measurements carried out for this study. Soil was revealed to be mostly clayey sand. Geostatistical analysis results showed that spatial variability of soil properties in both vertical and horizontal directions could be achieved from the electrical resistivity measurements. For this study area, it was shown that 9 m and 4 m were the sizes of the essential spatial structures in the data in the horizontal and vertical directions respectively. Another finding of interest was a second order trend in the resistivity data in both the horizontal and vertical directions that can be due to the decrease in resistivity with depth due to soil compression. All in all, the slope has been better understood with the merging of data and the aspects that require further investigation have been clearly depicted.

Accurate geotechnical interpretation of residual soils in Singapore, ranging from weathered soil to weathered rock, becomes essential for numerous ongoing and potential underground construction activities. Nearly two thirds of Singapore is covered with residual soils, consisting of the Bukit Timah granitic formation and the Jurong sedimentary formation, hence making its interpretation crucial. For geotechnical site characterization, near surface geophysical techniques such as spectral analysis of surface waves (SASW) method and multi-channel analysis of surface waves (MASW) have been commonly employed. In terms of active source tests, seismic waves are estimated from an active seismic source (e.g., a sledge hammer) used to generate waves at the ground surface, based on a two-receiver configuration for the SASW method and a linear array of receivers in line for the MASW method. The passive MASW surface-wave technique, also called Micro-tremors array measurement, measures passive seismic waves using 2-D array receivers from micro-tremor and ambient vibrations generated from natural or artificial sources. The possible depth of investigation via the active MASW method is generally shallower than 30m due to the limited propagation of active-source energy, while that via the passive MASW method is deeper than 30m due to ambient sources with low-frequency nature. The field measurement of shear wave velocity (V_s) is a significant element for geotechnical design practices as well as seismic ground hazard evaluation. Also, it has been employed for various applications such as settlement analysis and soil structure interaction, underground cavity/anomaly detection, and ground compaction quality evaluation. In this study, active and passive MASW techniques are integrated to obtain the V_s profile of residual soils and examine the possibility of detecting bedrock depth in Singapore’s geologic context. The results of field experiments showed that this combined non-invasive MASW method can be considered as a cost efficient means to understand soil dynamic characteristics and estimate the bedrock location compared to other geophysical testing methods as well as conventional boring investigation.

In order to understand the permanent deformation and degradation of railway ballast under high speed train loading, a series of cyclic triaxial tests were conducted using large-scale cylindrical apparatus. The frequency was used from 5 Hz to 60 Hz corresponding to the train speeds from about 40 km/h to 400 km/h. Three types of permanent deformation mechanisms were observed in response to the applied cyclic loads, namely, plastic shakedown at relatively lower frequency, ratcheting at an increased frequency, and plastic collapse at higher frequencies. Correspondingly, four types of particle degradation were observed. The magnitudes of ballast deformation and degradation were found to increase with the frequency and number of load cycles. A critical train speed was identified. Moreover, a good correlation was obtained between particle breakage and volumetric strain under cyclic loading.

Slip along fractures or hydrothermal alternation may lead to formation of weak layers of soils intercalated between the existing rock layers. In this situation, characterization of the behavior of rock fractures requires consideration of a complicated interaction of mechanical properties and geometrical characteristics of the fracture, coupled together with the properties of infill materials. Of the most important parameters which may considerably affect the behavior of an infilled fractured rock are the hydraulic properties of the infill material. These properties reflect the water retention ability of the infill material and determine the meniscus arrangements between the particles. This paper presents a new testing approach to describe the hydraulic properties of an infilled fractured rock under different stress states and saturation conditions. In this regard, a modified triaxial test device was used to establish the characteristic relationship between the degree of saturation and suction referred to as the soil water retention curve (SWRC). The new testing approach incorporates the axis translation technique for suction control, a flow pump for the measurement of infill’s degree of saturation, and the digital image processing (DIP) technique for volume change measurements. Results of this study suggested that variations in hydraulic properties of infilled fractured rock do not always correspond to changes in properties of the infill materials, but can be a result of a complex interaction of several factors, including morphological details of the fracture surface and the thickness and properties of the infill materials.

Studies with large physical models are a vital link between the theoretical work and field applications provided that these models are designed to represent real structures where various types and levels of uncertainties can be incorporated. While comprehensive analytical and laboratory joint studies are ongoing at Qatar University, University of Central Florida and University of Alberta, this paper presents the initial findings of dynamic testing at Qatar University. A laboratory stadium structure (grandstand simulator) has been constructed at Qatar University. Capable of housing thirty spectators, Qatar University grandstand simulator is arguably the largest laboratory stadium in the world. The structure is designed in a way that several different structural configurations can be tested in laboratory conditions to enable researchers to test newly developed damage detection algorithms. The study presented in this paper covers the finite element modeling and modal testing of the test structure.

Large floor and stadium structures can be subjected to onerous dynamic loadings during concert events, which might result in excessive levels of vibration. These could result in adverse comments and concern from occupants of the structure and even raise concerns regarding damage caused by fatigue. Active control is a technology with potential applications for control of floor vibrations, which has previously been used to control relatively low level vibrations in floor structures caused by small numbers of pedestrians. This paper presents an application of the technology to much higher levels of vibrations caused by crowds of people jumping during concert events. A number of challenges arise related to the amount of force required and maintenance of control of relatively large inertial masses and potential solutions are presented in this work. Results are given that show the performance of such a system under realistic crowd loading.

With the current demand for micropiles as small diameter, high capacity deep foundation elements, limitations on the usable yield stress for the reinforcing steel impacts project foundation costs and construction schedules. This paper presents current and historical evidence supporting the improper application of strain compatibility theory to specialty foundation systems, and outlines design protocols and conditions in which high strength steel reinforcement (e.g., F_y=669 MPa to F_u=1034 MPa) may be safely used. The focus will be on the uncased load transfer zone (bond length) of micropiles. Historical research in structural mechanics of confined concrete columns has documented the significant increases in grout ductility due to confinement, from ϵ_c of 0.003 to 0.05. Current research specifically focused on micropiles indicated clearly that ϵ_c exceeds 0.006 with confinement similar to that of very dense soils, and exceeds 0.014 for confinement similar to that of medium strength rock. These experimental data fully corroborate structural mechanics data on confined columns and support the use of full yield stress of high strength reinforcing steels in working axial resistance calculations for the micropile bond length.

Subsurface conditions for a combined cycle combustion plant in Warren County, Virginia were dominated by karst geology. Active sinkholes, numerous soil-, water-, and air-filled voids in the limestone bedrock, and highly varying rock surfaces associated with karst activity were present. To better characterize the site conditions, an extensive subsurface investigation with multiple phases was performed. Specific design and construction approaches were developed and utilized based on the site conditions to ensure the foundations would properly support the structures. A foundation type selection matrix was developed based on the results of the geotechnical investigation and structure-specific characteristics to consistently evaluate and quantify the level of risk associated with the foundation type selected for each piece of equipment. The use of the foundation type selection matrix aided in selecting a combination of micropile supported foundations and shallow foundations based on the risk of failure associated with each structure. A load testing program and full-time construction observation were employed to confirm micropile design and construction.

Over several decades, the superstructure of the 100-year-old Butler Street Bridge in Pittsburgh, PA had become severely dilapidated. In addition, the ravine beneath the span had been used as a dump site for ash from the City’s Herr’s Island incinerator to the point where it was filled almost to the underside of the deck arch. In 2013, the owner, Pennsylvania Department of Transportation District 11-0, began work on a long-awaited new bridge to entirely replace the existing structure. Each bridge abutment was initially designed to be supported on rock-socketed caissons. The original work plan was to remove the entire bridge superstructure and existing abutments and backfill up to the bottom of the new abutments prior to installation of the caissons. This would necessitate excavation of some 6880 m³ (9,000 yd³) of incinerator ash that was deemed landfill-sensitive. In an effort to reduce excavation quantities and efficiently streamline shoring operations, as well as to alleviate potential foundation element alignment issues that could arise from caisson drilling in the steeply sloping rock, the general contractor sought input from an engineering consultant, which developed an alternative micropile foundation design. This paper discusses the initial design, the re-design and its construction advantages, and installation and testing of the micropile foundation system.

A 3-story office building, with a footprint of 40 m x 28 m located within an industrial facility has undergone excessive settlement. Approximately 5 months after pouring the concrete for the roof slab (construction about 80% complete) the building started to suffer excessive settlement of up to 300mm. The office building is founded on a 0.6m thick raft foundation. The soil conditions at the site (based on two preconstruction bore holes located at the diagonal corners of the footprint) consist of 1m of structural fill, followed by 3m of soft clay, underlain by 3m of loose to medium sand, in turn underlain by 3m of soft clay followed by 3m of medium sand underlain by a 4m thickness of very stiff clay underlain by a very dens layer of sand which extends deep to the end of the bore hole. Groundwater was about 1m from ground surface. The measured settlement ranged from 170mm to 300 mm resulting in a differential settlement of 130mm. As a result, cracks began to show on the walls, flooring, and other building structural elements. In addition, the office building was constructed at the same time as an adjacent deep excavation, involving an extensive deep dewatering system, was being constructed. The authors became involved in the remediation alternative and recomended additional investigation during construction of the building to: (1) assess the subsurface conditions more accurately, (2) determine the root cause of the settlement, and (3) to develop the design for the remedial measures. This paper will discuss the settlement time history and analyze how the dewatering process played a role in increasing the office building settlement. In addition, the remedial measures taken to reduce additional settlement to the building will be described and discussed. Settlement monitoring following the remedial measures indicated that the settlement was controlled and the construction of the building was completed without experiencing additional movement.

The design and construction of a world class opera house and performing arts center with acoustic perfection has been the dream of Orlando philanthropists, performing arts benefactors, and numerous supporters for many years. This presentation describes the approach to deciding the foundation design for a public-private-partnership (P3) project which is 100% dependant on support of the local government and private donations for construction financing and must build the lowest-cost, highest quality facility within well-defined budgetary constraints.

The new Florida Hospital for Women is located on the main campus and will provide a new era of high tech care for the women of Central Florida. The twelve story building includes a full basement and is situated on a tight urban site. A cast in place reinforced concrete flat plate structural framing system was selected. Column loads varied from 1800 to 3900 kips. The geotechnical field explorations included SPT borings and CPT soundings to about 100 feet deep. The subsoil consisted of medium dense sand followed by medium stiff clays and silty to clayey sands underlain by the Hawthorne Group soils. Iterative foundation design process was developed and executed between the structural and geotechnical engineers to design the most economical foundation system to support the building. Settlement analysis was performed utilizing numerical modeling to provide accurate subgrade reaction modulus. A soil mat foundation was selected which offered better stress distribution and minimized differential settlement; however total estimated settlements were in the order of 3 inches. The design team along with the owner agreed to take the risk of approving the building total and differential settlement and account for it in the final design. Few columns were instrumented and monitored for settlement throughout the construction process. Recorded settlements were in the order of 50% of the estimated settlements. This paper summarizes the structural components, the geotechnical aspects, foundation design, and construction challenges of the project.

The Wilshire Grand Redevelopment project in downtown Los Angeles includes the demolition of a 16-story hotel built in the early 1950s and the construction of a new 73-story tower that will be the tallest building in the western United States. The construction of the basement and foundation of the new tower required excavation up to 93 feet (28 m) deep. One side of the basement excavation, with an excavation height along that side of up to 57 feet (17 m) required placement of shoring within about 6 to 10 feet (1.8 to 3.0 m) horizontally from a 400-foot-long (122 m) section of the Los Angeles Metro Red Line subway tunnel. A monitoring and contingency plan was established for the shoring itself and the subway tunnel. The shoring monitoring included periodic surveying, slope inclinometers, load cells on tie-back anchors, and strain gauges on raker braces. Deflection and vibration monitoring was performed on the interior of the Red Line tunnel utilizing automated total survey machines installed in the tunnel; the monitoring system provided real time data and automated alerts were provided when threshold readings were exceeded. Presented herein is a description of: (1) deflection and earth loading criteria for monitoring; (2) response levels utilized during monitoring; (3) data transmission methodologies; (4) communication protocols; (5) installation of instruments; (6) evaluation of monitoring data; and (7) modifications to monitoring protocols during project.

The Wilshire Grand redevelopment project in downtown Los Angeles includes demolition of a 16-story hotel and construction of a new 73-story tower. Construction of the basement and foundation of the new tower required excavation up to 93 feet deep (28 m). The south side of the excavation, up to 57 feet deep (17 m), required placement of shoring within about 6 to 10 feet (1.8 to 3.0 m) horizontally away from a 400-foot-long (122 m) section of the closest of the existing Los Angeles Metro Red Line twin subway tunnels adjacent to the site. The tunnels were constructed using a 22-foot-diameter (6.7 m) digger shield, and were initially supported with expanded, precast concrete segments, with final lining consisting of cast-in-place reinforced concrete. The temporary shoring system for the deep excavation consists of soldier piles generally spaced at 8 feet (2.4 m) on center with multiple levels of tieback anchors extending above the subway tunnels. The bottommost level of bracing consisted of rakers supporting walers attached to the soldier beams because installation of tieback anchors at that level would conflict with the tunnels. Numerical analyses were performed to predict tunnel movement caused by the excavation and its effects on the train operations. This paper describes the numerical modeling and comparison of the predicted and observed tunnel responses to the deep excavation and new tower construction.

Tunneling is an exciting combination of science, art and professional skill and is the ultimate implementation of ground-structure interaction. The ground, be it soil or rock, is an integral part of the tunnel structure and plays a key role in resisting the loads created by excavating the tunnel. This paper discusses seven of the most critical design considerations for tunnel lining design and construction; namely ground conditions, ground-liner interaction, thrust-moment interaction, tunnel geometry, tunneling method, construction monitoring and initial versus final lining. Given below are discussions about each of these considerations.

Soil-structure interaction (SSI) analysis is completed for a relatively rigid, deeply embedded structure. The structure has a large excavated volume, approximately 200’ by 400’ in footprint and 140’ embedded. Eight different site conditions are considered for the analyses providing for a range of soil property types. Results are reported in terms of structural displacements relative to the basemat elevation. In this paper, the conditions that induce a racking type response versus an inertial response are discussed. For certain soil cases, a racking type response is observed where a change is apparent in the profile of relative displacements throughout the embedded height. The racking response indicates a distortional response of the structure as a whole. In other cases, an inertial response is observed where the displacement profile is rather uniform throughout the height of the structure.

The uplift performance of a novel piling system consisting of a spun-cast ductile iron (SCDI) tapered pile fitted with a lower helical plate, intended as an efficient foundation system for solar energy panels, is examined in this paper. Five SCDI tapered piles and two straight shafted steel piles were installed and tested at two different loading sequences in silty sand. The results showed that the tapered piles had higher uplift capacity and exhibited stiffer response at lower displacements compared to the straight shafted piles. In addition, it was observed that initial compressive loading caused a loose soil zone above the helical plate, which reduced the system stiffness at the start of the uplift loading, whereas the application of cyclic uplift loading increased the developed shaft stresses at lower displacement.

Expanding development of ground mount solar energy systems requires economic foundation systems that can support expected loads safely. The critical design loading for most ground mount solar systems in uplift from wind loading, especially for elevated systems that are designed to allow dual use of the land. A number of different types of foundations may be used to support the structural framework and resist uplift loading. Full-scale uplift tests taken to failure were performed on different foundations at five sites representing a range of soil conditions to illustrate the typical load capacity that can be achieved. The foundations included drilled piers, precast pedestals, driven steel H-piles, driven steel pipe piles and helical screw-piles. The results of load tests are presented along with a discussion of the potential advantages and limitations of the various types of foundations.

According to FHWA, more than 36,000 bridges over waterways (riverine and tidal) are identified as having unknown foundations. Unknown bridge foundations pose a significant problem to the assessment of hydraulic and seismic vulnerability and post-hazard evaluation of bridges. In addition, bridge foundations reuse could become a viable option in the replacement of structurally deficient superstructures, potentially providing technical, economic, time and environmental benefits. Characterization and evaluation of existing bridge substructures has become an essential issue for the safety and serviceability of bridges. In recent years experimental modal analysis has become an effective tool for bridge condition assessment and system identification. However, many studies tend to emphasize dynamic testing and analysis of bridge superstructures with little consideration given to bridge substructure and their foundations. In this paper, a 3 non-continuous spans bridge with concrete deck and steel girders is used as a case study to investigate the possibility of characterization and condition evaluation of the substructure system leveraging dynamic testing methods. MIMO impact testing and operating modal analysis was operated on one of the piers of this bridge. Corresponding modal identification algorithms including CMIF and Bayesian operational modal analysis method is discussed. Modal parameters, including modal frequencies and mode shapes obtained from two experimental modal analysis methods, are presented and compared.

There are great economic incentives motivating the reuse of existing foundations when deteriorated and damaged superstructures are replaced. The increasing reuse of existing bridge foundations warrants investigation into verifying foundation performance and condition of in service bridge foundations. A method is proposed which characterizes the load-response behavior of existing bridge foundations during daily vehicular loading without impeding traffic. It uses a limited number of substructure response measurements from an in service bridge taken during daily traffic heavy truck loadings. The results from this method can be used to verify the vertical, horizontal and rotational load-deformation behavior during daily loadings. Potential applications for the results obtained through this approach are: the detection of structural damage, identification of scour, identification of unknown foundations, and validation the load-deformation behavior predicted by finite element analysis. While loading during the tests would be limited to the magnitude which is caused by daily truck passage, the behavior observed from this loading can be used to update the parameters governing soil behavior which will lead to an improved assessment of the foundation behavior during failure loading or extreme events. A preliminary study is presented as a feasibly study for future use of the proposed method for bridge foundation stiffness identification using substructure measurements.

Damage detection and localization from dense sensing networks have been studied in structural health monitoring research community over the past few decades. However, with inevitable rapid growth of monitoring data, data transmission and processing from densely located sensors has become challenging due to the power constraints and computational costs. To address this problem, an image-based damage detection framework with compressive sensing approach is proposed in this paper. This method implements compressive sensing by exploiting the sparsity of the samples in discrete cosine transform (DCT). The suggested methodology divides the sensor network space into blocks and selects subsets of sensors from each block. The selected sensors are regularized through a greedy algorithm called orthogonal matching pursuit (OMP) to obtain the sparsest representation of the samples in DCT domain. Avoiding the recovery of the original signal, the change statistics of DCT coefficients are employed to estimate damage existence and location. Performance of this method with a method previously proposed by the authors based on hierarchical sampling in the sensor network, change point analysis, and Bayesian probability estimation is compared through damage localization of a cracked steel gusset connection model.

Assessing the potential damage to nearby existing structures from vibrations induced during foundation construction is a complex task. The current practices to prevent damage to existing structures suggest limiting the peak particle velocity (PPV) created during foundation construction activities. Numerous existing structures have suffered damage from foundation construction activities even after full compliance to the current methodology of limiting the PPV. This paper presents an approach to safeguard existing structures adjacent to construction activity through real time dynamic structural evaluation.

Throughout the world, many highway workers and road users face safety hazards associated with bridges. ASCE estimates that one in nine of the nation’s bridges are rated as structurally deficient, with an average age of 42 years. In an effort to reduce the risks associated with bridges, the Federal Highway Administration (FHWA) requires states to perform a detailed, visual inspection and inventory of all federal-aided highway system bridges once every two years. At times, mandatory inspections are costly and dangerous, as inspectors need to stand in platform trucks, bucket trucks, or under-bridge inspection vehicles in order to access and view necessary bridge elements. Furthermore, some inspections require extensive climbing, temporary scaffolding and ladders, or rescue boats. Unmanned aircraft system (UAS) technology provides a cost-effective and safe method for remotely performing visual inspections and inventorying of bridges. UASs are capable of flying a pre-programmed flight path, and can carry high resolution digital cameras and/or other sensors. During flights, operators can view live video from the camera on a monitor or through live video goggles. In addition, digital imagery collected during flights can be mosaicked, georeferenced, and converted into 3D point clouds for detailed spatial inventorying. This paper presents the methodology and results of inspections of a bridge in Oregon using a multicopter UAS. Because multicopters can be flown close to objects, are easy to maneuver, and can hover in place, high-resolution remote sensing data can be collected from multiple advantageous viewing angles. Such data is similar to what can be seen visually by an inspector at arm’s length from the bridge. Recommendations for safe and effective flights are given, and the capabilities and limitations of UAS bridge inspections are discussed. It will be shown that today’s UAS technology has great potential for performing remote and safe, visual inspections of structures.

This paper focuses on the development of joint seismic and scour fragility function of a three-story existing steel moment resisting frame structure in the Central United States. The structure dimensions with beam and column details were obtained from the design plan from the building owner. With all the information, a three-dimensional (3D) model of the structure with soil springs reflecting the soil-structure interaction behaviors during an earthquake was created through commercially available finite element software. To account for joint seismic and scour risk, a total of forty eight synthetic ground motions having different spectral accelerations (S_a) were used, and the soil springs were progressively removed. Numerous nonlinear time history analyses reflecting the effects of scour effects by adjusting the removed soil spring number was conducted to determine peak inter-story drifts of the structure simultaneously subjected to the ground motions. Federal Emergency Management Agency (FEMA)-based three performance levels (i.e., immediate occurrence, life safety, and collapse prevention) were considered for the creation of joint seismic and scour fragility functions. Significant findings show that the joint seismic and scour vulnerability of the structure increased as they become more damaged due to the reduced resistant forces from the removal of soil springs over a broad spectrum of S_a.

Countries around the world are proactively planning to efficiently and effectively mitigate destruction, and maximum resiliency during a natural hazard. Yet, after each disastrous and most often fatal event, governments are learning how to improve their resiliency plans. This paper examines the recovery phase of natural disasters in developing countries by taking a comparative view of the same process in developed countries. The impact of such catastrophic events on our buildings and infrastructure leave communities in a state of reclamation for years. Following such disasters, strategies have been implemented to recover but also to improve the response for future events in both developed and developing countries. To explore lessons learned across these strategies, this paper examines the disaster and recovery efforts of three natural disasters: (1) 2004 Sumatra Earthquake and Tsunami that occurred in Sumatra, Indonesia; (2) Hurricane Katrina that occurred in 2005 in New Orleans, LA (United States); and (3) 2010-2011 Canterbury/Christchurch Earthquake sequences that have taken place in Christchurch, New Zealand. The post disaster recovery programs are compared and contrasted, as well as the nature and effect of the disaster on the local communities. This research aims to offer new perspective on the approach to disaster recovery while simultaneously offering engineers a prized role to think beyond the code and evaluate a broad range of perspectives towards engineering solutions for disaster resilience. Lastly, this paper aims to uncover any potential cross-pollination of ideas between developed and developing nations to refine future solutions towards disaster resilience.

Collapse performance of nine existing multi-story buildings have been investigated through field experiments and computational modelling. Masonry, reinforced concrete and steel frame buildings have been tested. Most of the test buildings were located on the Ohio State University campus. Single or multiple first-story columns were physically removed from each building during the experiments. The data produced in this research has been a valuable addition to the state of knowledge on progressive collapse of buildings because experimental evidence from full-scale structures is either very limited or does not exist. The main goal of field experiments was to simulate the dynamic and static response of buildings that may experience progressive collapse after sudden loss of column(s). Another objective was to investigate how the internal forces would be redistributed within the building after column loss. Experimental data is used to evaluate the design methods and analysis procedures recommended in current design guidelines. Two and three-dimensional building models were analyzed to simulate the progressive collapse response. Computational models and simulations were compared with the experimental data from the field tests. This study showed robustness of existing buildings and potential contribution of structural components to collapse resistance.

The slew of high profile engineering calamities in the past decade has demonstrated the disastrous consequence of progressive collapse. Precast concrete structures may have a higher vulnerability to progressive collapse compared to cast-in-situ structures due to possible lower integrity in connections and joints. However, compared to cast-in-situ structures, limited studies have been carried out to evaluate the behavior of precast structures for prevention of progressive collapse. For this purpose, a series of three-dimensional (3D) precast structures with different connection types were tested in Nanyang Technological University, Singapore. The effects of varying the types of slab-beam connections and beam-column joints on the progressive collapse performance of precast concrete structures were evaluated. The preliminary test results were presented and the failure modes and possible load resisting mechanisms of precast structures to resist progressive collapse were discussed.

This paper describes the evaluation of several steel building configurations for robustness. The buildings studied were inspired from two prototype buildings which employed “stiff-story” trusses to transfer loads due to multi-bay spans and cantilevers. The UFC 4-023-03 guidelines were followed to perform an elastic alternate path analysis and to evaluate various framing configurations for robustness. Indices were then developed to help identify, on a preliminary basis, which configurations are more robust. These indices, named the support factor and the bracing factor, provide a simple measurement of robustness and efficiency in the framing system of the building. Results from the study show that stiff stories integrated with the lateral force resisting system can be very effective in increasing robustness.

It has been shown in previous full-scale experiments on steel moment frame connections that fracture initiation is typically not associated with an observable loss of moment carrying capacity. Although low cycle fatigue models have been used to predict fracture initiation, most low cycle fatigue models do not capture fracture propagation. To assess the performance of steel seismic force resisting systems, and in particular steel moment resisting frames as subjected to large earthquakes, it is critical to understand fracture propagation. The damage plasticity model is a local approach to model material failures and has been used in limited studies found in the literature. Finite element models are created using the software LS-DYNA that incorporate the damage plasticity model to capture low cycle fatigue fracture initiation and propagation through element removal. Test data from full-scale moment connection tests conducted previously by the authors are used in this study to evaluate the modeling approach. Observations about the locations of fracture initiation, cycle in which fracture initiated and the evolution of fracture propagation is documented and compared to the experimental results.

The purpose of this paper is to (1) develop an approach to determine the serviceability behavior of concrete discontinuity regions and (2) refine existing methods for processing digital images and automating the collection of crack and displacement data. A research program currently underway at Northern Arizona University is seeking to correlate maximum crack width and crack area to the internal strain energy estimated from a representative strut-and-tie model. This effort is accomplished by testing twelve concrete deep beams with a 10×20 in. cross-section. Crack width, crack area, and deformation data establishes serviceability behavior. Preliminary findings indicate it is possible to determine serviceability behavior using internal strain energy in strut and tie models. These findings represent an improved design methodology engineers can use to perform serviceability design of their reinforced discontinuity regions.

With progress in the field of civil construction projects especially in geotechnic projects, various construction methods have been introduced to fulfill project purposes. Underground structures and deep excavations, as essential part of construction of main structure, are also of advancing projects. Applying various construction methods is contingent on the possibility of achieving a suitable and correct design method. In some cases it is needed to combine different construction methods to reach a suitable design. This article studies a three-storey shallow-buried urban metro station using diaphragm wall construction method. Some of the challenges in this study are the slab-wall connection type and the geometry of the bottom slab (foundation), as a flat or arch slab, and concluding an optimum design. In this study the analysis is based on finite element method. In a similar state of slab-wall connection the structure is analyzed under two conditions: flat and arch bottom slab; and analysis results are compared and contrasted. The internal forces and moments in the structural members are then compared in static and seismic analysis. By studying the analysis results, slab geometry and connection type are chosen according to the internal forces and structural behavior. The analysis showed that in the structure with arch bottom slab the internal forces (moment and shear) in the wall especially in the first floor are greater compared to that of the structure with flat bottom slab. Moreover, the analyses and study of connection types indicted that the optimum design is reached when the connection of floor slabs to the wall is of fixed type and the connection of invert to the wall are pinned.

Retaining walls supporting lateral earth pressure over more than 6 meter depth may require a wide foundation to satisfy all stability requirements. In urban areas excavation width can be of concern when heavy traffic and nearby existing structures can be seriously affected during project construction period. The design choice of placing the retaining wall on a narrow beam supported by piles is well suited to urban areas where space constraints and damage to adjacent structures are major considerations. This work investigated design approaches using two methods in order to arrive at an optimum geometric design. The first approach treated the retaining wall and beam system as a separate unit and piles as another unit supporting lateral load and moment at the top in addition to axial and frictional loads. The second approach considered monolithic system in which both the piles and retaining walls are treated as a one unit. SAP 2000 program was used to compute all moments and shear forces based on the same input data implemented in the first approach. The outputs of the two approaches are compared and discussed and validation of the final design output is reviewed. Recommendations on selecting geotechnical design parameters for the two approaches are presented.

The most technically complex aspect of the Los Angeles County Metropolitan Transportation Authority (LACMTA) Regional Connector Transit Corridor (RCTC) project in Downtown Los Angeles is the mined crossover cavern, the largest tunneled excavation contemplated in Los Angeles, to be constructed using sequential excavation methods (SEM). This paper describes the integrated geostructural design and construction approach developed to maximize construction productivity while ensuring the stability and performance of existing infrastructure.

Significant effort has been placed on the determination of swelling properties of expansive soils, such as swell pressure and swell potential. However, there are only a limited number of studies of expansive soil response that include the effect of desiccation cracking; most studies and methods of analysis have simply neglected the effect of cracks. At the same time that cracks provide a path for flow of water under positive head, the crack network in an expansive soil functions as swell-absorbent media (due to open spaces within the soil) which can reduce the total amount of vertical swell that the soil would experience. In this study, a laboratory investigation was carried out to quantitatively evaluate the effect of cracks on swell potential and swelling pressure. The presence of desiccation cracks was found to reduce the amount of swell and also reduce the swell pressure compared to intact, uncracked, specimens. The percentage reduction of swell potential and swell pressure was found to be a function of the volume of cracks and the applied net normal stress.

Steady-state infiltration technique can be used to develop a uniform degree of saturation profile in centrifuge physical models. This enables researchers to study different characteristics of partially-saturated soils. Although large-scale suction-controlled experiments have been conducted successfully, they involved inevitable challenges. Infiltrating water through soil-structure systems in the centrifuge could lead to non-uniform flow paths. Use of miniature pore pressure transducers (PPT) to capture changes of suction requires careful attention to avoid desaturation of the sensors. Suction scaling factor were proven to be unity for larger centrifuges (i.e. when the ratio between centrifuge arm and specimen height is greater than 10), but this issue has not been explored for smaller centrifuges. Seismic settlement of unsaturated soil layers in a geotechnical centrifuge contains limitations that should be considered when the results are interpreted.

Mechanical properties of soil and soil-pile interface are critical for the rational analysis and design of pile foundations in unsaturated soils. This study presents experimental results of model pile tests performed in two different sands and a glacial till with different values of soil suction. Numerical modeling studies using commercial software PLAXIS 2D are conducted to simulate the measured load-settlement behavior of the model piles. Soil and interface mechanical properties at various soil suction levels used in the modeling are estimated using a simple approach that only requires the measured mechanical properties at saturation condition and the soil-water characteristic curve (SWCC). There is good agreement between the measured and modeled load-settlement behavior of model piles. The simple approach proposed in this paper is promising for use in conventional geotechnical engineering practice for the design of single piles in unsaturated soils.